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Digest of Education Statistics: 2017
Digest of Education Statistics: 2017

NCES 2018-070
January 2018


Table 209.10. Number and percentage distribution of teachers in public and private elementary and secondary schools, by selected teacher characteristics: Selected years, 1987-88 through 2015-16
[Standard errors appear in parentheses]
Selected teacher characteristic Number of teachers (in thousands) Percentage distribution of teachers
1987-88 1990-91 1999-2000 2003-04 2007-08 2011-12 2015-16 1987-88 1990-91 1999-2000 2003-04 2007-08 2011-12 2015-16
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Public schools                                                                                    
Total 2,323   (13.2) 2,559   (20.7) 3,002   (19.4) 3,251   (29.2) 3,405   (44.0) 3,385   (41.4) 3,827   (49.5) 100.0   (†) 100.0   (†) 100.0   (†) 100.0   (†) 100.0   (†) 100.0   (†) 100.0   (†)
Sex                                                                                    
Male 685   (6.8) 719   (11.2) 754   (10.7) 813   (13.3) 821   (20.4) 802   (22.2) 897   (18.1) 29.5   (0.22) 28.1   (0.31) 25.1   (0.30) 25.0   (0.32) 24.1   (0.47) 23.7   (0.49) 23.4   (0.34)
Female 1,638   (10.1) 1,840   (14.7) 2,248   (16.0) 2,438   (23.5) 2,584   (34.6) 2,584   (30.5) 2,930   (39.1) 70.5   (0.22) 71.9   (0.31) 74.9   (0.30) 75.0   (0.32) 75.9   (0.47) 76.3   (0.49) 76.6   (0.34)
                                                                                     
Race/ethnicity                                                                                    
White1 2,018   (12.6) 2,214   (20.0) 2,532   (17.2) 2,702   (30.1) 2,829   (38.7) 2,773   (30.5) 3,067   (41.9) 86.9   (0.24) 86.5   (0.29) 84.3   (0.30) 83.1   (0.53) 83.1   (0.53) 81.9   (0.53) 80.1   (0.34)
Black1 191   (4.6) 212   (6.4) 228   (6.0) 257   (11.0) 239   (15.8) 231   (12.1) 256   (8.8) 8.2   (0.19) 8.3   (0.25) 7.6   (0.19) 7.9   (0.34) 7.0   (0.45) 6.8   (0.31) 6.7   (0.21)
Hispanic1 69   (2.6) 87   (4.5) 169   (6.4) 202   (11.3) 240   (16.6) 264   (13.4) 338   (9.2) 3.0   (0.11) 3.4   (0.17) 5.6   (0.20) 6.2   (0.34) 7.1   (0.46) 7.8   (0.37) 8.8   (0.22)
Asian1,2 21   (1.1) 27   (1.7) 48   (2.7) 42   (2.5) 42   (7.2) 61   (7.3) 86   (3.9) 0.9   (0.05) 1.0   (0.06) 1.6   (0.09) 1.3   (0.08) 1.2   (0.21) 1.8   (0.21) 2.3   (0.09)
Pacific Islander   (†)   (†)   (†) 6   (0.8) 6   (1.3) 5   (1.4) 9   (1.1)   (†)   (†)   (†) 0.2   (0.03) 0.2   (0.04) 0.1   (0.04) 0.2   (0.03)
American Indian/
      Alaska Native1
24   (1.3) 20   (1.4) 26   (1.9) 17   (1.2) 17   (1.9) 17   (2.9) 17   (1.5) 1.0   (0.06) 0.8   (0.05) 0.9   (0.06) 0.5   (0.04) 0.5   (0.06) 0.5   (0.08) 0.4   (0.04)
Two or more races   (†)   (†)   (†) 24   (2.2) 31   (2.9) 35   (3.7) 54   (2.8)   (†)   (†)   (†) 0.7   (0.07) 0.9   (0.09) 1.0   (0.11) 1.4   (0.07)
                                                                                     
Age                                                                                    
Under 30 313   (5.0) 257   (5.7) 509   (9.2) 540   (27.4) 612   (22.4) 518   (15.9) 574   (11.4) 13.5   (0.19) 10.0   (0.23) 17.0   (0.28) 16.6   (0.84) 18.0   (0.61) 15.3   (0.44) 15.0   (0.23)
30 to 39 823   (7.7) 684   (10.8) 661   (9.8) 798   (14.5) 898   (16.8) 979   (19.3) 1,090   (17.0) 35.4   (0.30) 26.7   (0.35) 22.0   (0.29) 24.5   (0.38) 26.4   (0.39) 28.9   (0.53) 28.5   (0.28)
40 to 49 762   (7.4) 1,034   (13.3) 953   (10.3) 840   (14.3) 808   (19.2) 849   (19.2) 1,050   (17.7) 32.8   (0.25) 40.4   (0.37) 31.8   (0.32) 25.9   (0.38) 23.7   (0.47) 25.1   (0.51) 27.4   (0.29)
50 to 59 357   (5.7) 477   (8.6) 786   (12.6) 942   (26.0) 879   (21.1) 783   (20.5) 823   (14.4) 15.4   (0.23) 18.7   (0.29) 26.2   (0.35) 29.0   (0.74) 25.8   (0.51) 23.1   (0.49) 21.5   (0.23)
60 and over 68   (2.5) 107   (4.1) 93   (4.0) 131   (4.8) 207   (10.3) 256   (13.2) 290   (7.5) 2.9   (0.11) 4.2   (0.16) 3.1   (0.13) 4.0   (0.14) 6.1   (0.29) 7.6   (0.34) 7.6   (0.17)
                                                                                     
Highest degree earned                                                                                    
Less than bachelor's 15   (1.0) 17   (1.2) 20   (1.3) 35   (2.5) 27   (2.1) 128   (8.6) 93   (3.7) 0.7   (0.04) 0.7   (0.05) 0.7   (0.04) 1.1   (0.08) 0.8   (0.06) 3.8   (0.24) 2.4   (0.10)
Bachelor's 1,214   (9.8) 1,327   (11.7) 1,560   (15.8) 1,651   (22.8) 1,612   (28.8) 1,350   (21.1) 1,550   (23.4) 52.3   (0.28) 51.9   (0.31) 52.0   (0.40) 50.8   (0.56) 47.4   (0.59) 39.9   (0.52) 40.5   (0.34)
Master's 932   (8.5) 1,077   (13.5) 1,257   (13.9) 1,331   (21.7) 1,517   (27.8) 1,614   (29.1) 1,812   (26.3) 40.1   (0.30) 42.1   (0.34) 41.9   (0.38) 40.9   (0.56) 44.5   (0.55) 47.7   (0.57) 47.3   (0.34)
Education
      specialist3
146   (3.4) 118   (5.3) 143   (5.2) 195   (6.8) 218   (8.6) 257   (9.7) 323   (8.8) 6.3   (0.14) 4.6   (0.20) 4.7   (0.17) 6.0   (0.19) 6.4   (0.25) 7.6   (0.27) 8.4   (0.18)
Doctor's 16   (1.2) 20   (1.7) 22   (1.8) 38   (3.5) 30   (2.7) 37   (4.0) 49   (3.1) 0.7   (0.05) 0.8   (0.07) 0.7   (0.06) 1.2   (0.11) 0.9   (0.08) 1.1   (0.11) 1.3   (0.08)
                                                                                     
Years of teaching
      experience
                                                                                   
Less than 3 145   (3.2) 185   (4.8) 325   (7.7) 339   (36.6) 392   (18.1) 244   (8.5) 380   (8.8) 6.2   (0.14) 7.2   (0.19) 10.8   (0.24) 10.4   (1.13) 11.5   (0.48) 7.2   (0.24) 9.9   (0.19)
3 to 9 568   (6.3) 596   (9.4) 854   (12.3) 1,043   (14.1) 1,125   (19.6) 1,104   (20.6) 1,083   (17.1) 24.4   (0.22) 23.3   (0.30) 28.5   (0.37) 32.1   (0.33) 33.0   (0.52) 32.6   (0.52) 28.3   (0.30)
10 to 20 1,072   (8.7) 1,056   (11.8) 865   (10.1) 946   (21.5) 1,017   (24.3) 1,265   (21.0) 1,504   (23.0) 46.1   (0.27) 41.3   (0.35) 28.8   (0.33) 29.1   (0.58) 29.9   (0.57) 37.4   (0.53) 39.3   (0.31)
Over 20 539   (6.1) 721   (10.6) 958   (13.5) 922   (27.9) 871   (23.9) 772   (23.8) 860   (15.8) 23.2   (0.23) 28.2   (0.30) 31.9   (0.36) 28.4   (0.81) 25.6   (0.62) 22.8   (0.54) 22.5   (0.27)
                                                                                     
Level of instruction4                                                                                    
Elementary 1,292   (9.5) 1,442   (11.8) 1,602   (13.5) 1,716   (25.8) 1,725   (37.1) 1,726   (20.2) 1,908   (41.2) 55.6   (0.33) 56.3   (0.40) 53.3   (0.42) 52.8   (0.66) 50.7   (0.91) 51.0   (0.65) 49.8   (0.96)
General 788   (7.4) 887   (10.6) 1,042   (12.5) 1,130   (29.8) 1,100   (26.5) 1,078   (22.1) 1,166   (27.4) 33.9   (0.29) 34.6   (0.39) 34.7   (0.41) 34.8   (0.86) 32.3   (0.70) 31.8   (0.71) 30.5   (0.65)
Arts/music 116   (3.0) 110   (4.3) 99   (3.7) 101   (5.3) 103   (6.6) 82   (5.4) 108   (4.5) 5.0   (0.13) 4.3   (0.17) 3.3   (0.12) 3.1   (0.17) 3.0   (0.19) 2.4   (0.16) 2.8   (0.11)
English 60   (2.3) 72   (3.8) 66   (3.8) 70   (5.1) 104   (9.9) 92   (6.9) 138   (5.2) 2.6   (0.10) 2.8   (0.14) 2.2   (0.13) 2.2   (0.16) 3.0   (0.29) 2.7   (0.21) 3.6   (0.13)
ESL/bilingual 18   (1.1) 20   (1.3) 28   (1.8) 25   (3.6) 24   (3.3) 51   (6.8) 53   (3.1) 0.8   (0.05) 0.8   (0.05) 0.9   (0.06) 0.8   (0.11) 0.7   (0.10) 1.5   (0.20) 1.4   (0.08)
Health/physical ed. 56   (2.0) 66   (3.2) 57   (3.5) 73   (5.0) 63   (6.0) 79   (8.1) 70   (3.2) 2.4   (0.09) 2.6   (0.12) 1.9   (0.12) 2.2   (0.15) 1.8   (0.18) 2.3   (0.23) 1.8   (0.08)
Mathematics 31   (2.0) 30   (1.9) 23   (2.4) 19   (2.3) 28   (3.8) 32   (6.5) 42   (2.6) 1.3   (0.09) 1.2   (0.08) 0.8   (0.08) 0.6   (0.07) 0.8   (0.11) 0.9   (0.19) 1.1   (0.07)
Science 18   (1.5) 21   (1.9) 11   (1.3) 19   (3.0) 15   (3.4) 18   (3.3) 25   (1.9) 0.8   (0.06) 0.8   (0.07) 0.4   (0.04) 0.6   (0.09) 0.4   (0.10) 0.5   (0.10) 0.7   (0.05)
Special education 168   (3.9) 176   (5.9) 227   (5.6) 240   (20.6) 230   (13.0) 239   (10.3) 247   (6.9) 7.2   (0.16) 6.9   (0.23) 7.6   (0.18) 7.4   (0.63) 6.7   (0.37) 7.1   (0.31) 6.4   (0.16)
Other elementary 37   (2.4) 60   (3.2) 49   (3.5) 40   (3.5) 58   (4.2) 55   (5.2) 59   (3.1) 1.6   (0.10) 2.4   (0.12) 1.6   (0.12) 1.2   (0.11) 1.7   (0.12) 1.6   (0.15) 1.5   (0.08)
Secondary 1,031   (10.5) 1,118   (16.5) 1,401   (17.7) 1,534   (26.0) 1,680   (39.0) 1,659   (37.8) 1,920   (47.2) 44.4   (0.33) 43.7   (0.40) 46.7   (0.42) 47.2   (0.66) 49.3   (0.91) 49.0   (0.65) 50.2   (0.96)
Arts/music 73   (2.0) 74   (2.3) 110   (3.4) 112   (4.1) 121   (6.2) 121   (5.6) 150   (5.3) 3.1   (0.09) 2.9   (0.08) 3.7   (0.11) 3.4   (0.12) 3.6   (0.18) 3.6   (0.14) 3.9   (0.13)
English 171   (3.2) 195   (5.1) 245   (5.1) 269   (9.0) 306   (10.0) 289   (9.9) 339   (9.1) 7.4   (0.12) 7.6   (0.18) 8.2   (0.15) 8.3   (0.27) 9.0   (0.27) 8.5   (0.25) 8.9   (0.20)
ESL/bilingual 6   (0.5) 10   (0.7) 16   (1.2) 18   (2.5) 21   (2.5) 20   (2.4) 25   (1.9) 0.3   (0.02) 0.4   (0.03) 0.5   (0.04) 0.6   (0.08) 0.6   (0.07) 0.6   (0.07) 0.7   (0.05)
Foreign language 43   (1.2) 52   (2.4) 71   (2.4) 73   (3.3) 78   (5.0) 88   (4.5) 95   (4.0) 1.9   (0.05) 2.0   (0.09) 2.4   (0.08) 2.3   (0.10) 2.3   (0.14) 2.6   (0.12) 2.5   (0.10)
Health/physical ed. 76   (2.4) 76   (2.2) 99   (3.1) 102   (4.3) 119   (5.7) 101   (3.9) 108   (3.7) 3.3   (0.10) 3.0   (0.08) 3.3   (0.10) 3.1   (0.12) 3.5   (0.16) 3.0   (0.11) 2.8   (0.09)
Mathematics 139   (2.5) 155   (4.3) 207   (4.5) 213   (5.5) 252   (9.1) 250   (7.5) 281   (8.4) 6.0   (0.10) 6.0   (0.15) 6.9   (0.14) 6.5   (0.17) 7.4   (0.25) 7.4   (0.19) 7.3   (0.18)
Science 115   (2.9) 128   (4.0) 169   (4.0) 189   (6.8) 195   (8.3) 209   (6.1) 232   (6.5) 4.9   (0.11) 5.0   (0.15) 5.6   (0.12) 5.8   (0.20) 5.7   (0.24) 6.2   (0.16) 6.1   (0.15)
Social studies 118   (2.4) 124   (3.3) 163   (4.4) 178   (5.7) 209   (9.9) 197   (6.3) 232   (7.5) 5.1   (0.10) 4.8   (0.12) 5.4   (0.14) 5.5   (0.16) 6.1   (0.27) 5.8   (0.16) 6.1   (0.17)
Special education 100   (2.2) 113   (3.5) 113   (2.8) 174   (7.5) 165   (9.7) 191   (12.2) 207   (6.0) 4.3   (0.09) 4.4   (0.13) 3.8   (0.09) 5.4   (0.23) 4.9   (0.28) 5.7   (0.32) 5.4   (0.14)
Vocational/
      technical
166   (3.0) 160   (3.7) 161   (3.5) 169   (5.7) 164   (6.3) 147   (5.7) 172   (6.5) 7.1   (0.12) 6.3   (0.12) 5.4   (0.10) 5.2   (0.17) 4.8   (0.17) 4.3   (0.16) 4.5   (0.15)
Other secondary 25   (1.3) 30   (1.5) 47   (2.0) 36   (2.1) 47   (3.4) 46   (4.0) 80   (3.4) 1.1   (0.06) 1.2   (0.06) 1.6   (0.07) 1.1   (0.06) 1.4   (0.10) 1.4   (0.12) 2.1   (0.09)
                                                                                     
Private schools                                                                                    
Total 307   (8.5) 356   (7.2) 449   (10.6) 467   (10.3) 490   (9.2) 465   (11.1)   (†) 100.0   (†) 100.0   (†) 100.0   (†) 100.0   (†) 100.0   (†) 100.0   (†)   (†)
Sex                                                                                    
Male 67   (3.3) 82   (3.3) 107   (3.8) 110   (8.4) 127   (4.6) 117   (6.9)   (†) 21.8   (0.86) 22.9   (0.74) 23.9   (0.48) 23.6   (1.93) 26.0   (0.78) 25.2   (1.33)   (†)
Female 240   (7.2) 275   (5.8) 342   (7.7) 357   (14.3) 362   (7.7) 348   (10.1)   (†) 78.2   (0.86) 77.1   (0.74) 76.1   (0.48) 76.4   (1.93) 74.0   (0.78) 74.8   (1.33)   (†)
                                                                                     
Race/ethnicity                                                                                    
White1 285   (8.3) 329   (7.0) 402   (9.6) 411   (12.0) 423   (8.8) 411   (11.1)   (†) 92.8   (0.50) 92.2   (0.46) 89.5   (0.42) 88.0   (0.99) 86.4   (0.80) 88.3   (0.69)   (†)
Black1 7   (0.8) 9   (1.0) 17   (1.4) 19   (2.9) 20   (2.2) 17   (2.4)   (†) 2.3   (0.27) 2.7   (0.28) 3.7   (0.29) 4.0   (0.65) 4.0   (0.44) 3.6   (0.54)   (†)
Hispanic1 9   (1.1) 12   (1.0) 21   (1.5) 23   (3.1) 29   (2.1) 24   (2.4)   (†) 2.8   (0.36) 3.3   (0.26) 4.7   (0.30) 4.8   (0.71) 5.9   (0.38) 5.2   (0.51)   (†)
Asian1,2 4   (0.8) 5   (0.6) 7   (0.6) 9   (1.0) 11   (1.5) 9   (1.4)   (†) 1.2   (0.26) 1.5   (0.18) 1.6   (0.14) 1.8   (0.20) 2.2   (0.29) 1.8   (0.31)   (†)
Pacific Islander   (†)   (†)   (†)   (†)   (†)   (†)   (†)   (†)   (†)   (†) 0.2 ! (0.07) 0.3 ! (0.14)   (†)   (†)
American Indian/
      Alaska Native1
3   (0.4) 1   (0.3) 2   (0.4)   (†)   (†)   (†)   (†) 0.9   (0.12) 0.4   (0.09) 0.6   (0.08)   (†)   (†)   (†)   (†)
Two or more races   (†)   (†)   (†) 3 ! (1.4) 4   (0.6) 4   (0.9)   (†)   (†)   (†)   (†) 0.6 ! (0.28) 0.7   (0.12) 0.8   (0.19)   (†)
                                                                                     
Age                                                                                    
Under 30 67   (2.6) 60   (2.2) 87   (3.1) 88   (3.7) 80   (3.9) 78   (6.8)   (†) 21.8   (0.77) 16.7   (0.61) 19.3   (0.43) 18.9   (0.78) 16.3   (0.67) 16.7   (1.48)   (†)
30 to 39 106   (3.6) 100   (4.0) 101   (3.2) 103   (5.8) 109   (5.2) 112   (6.2)   (†) 34.5   (0.81) 28.1   (0.78) 22.4   (0.50) 22.0   (1.36) 22.3   (0.91) 24.0   (1.07)   (†)
40 to 49 84   (3.4) 121   (3.1) 131   (4.2) 119   (7.1) 116   (3.6) 110   (6.3)   (†) 27.4   (0.78) 33.9   (0.74) 29.2   (0.62) 25.4   (1.41) 23.8   (0.65) 23.8   (1.06)   (†)
50 to 59 34   (2.2) 53   (2.3) 106   (3.2) 121   (11.1) 128   (4.5) 99   (5.0)   (†) 11.1   (0.57) 14.8   (0.55) 23.5   (0.46) 25.8   (2.07) 26.2   (0.87) 21.3   (1.06)   (†)
60 and over 16   (1.7) 23   (1.6) 25   (1.2) 37   (4.7) 56   (3.1) 66   (5.0)   (†) 5.3   (0.49) 6.4   (0.41) 5.7   (0.24) 8.0   (0.99) 11.5   (0.62) 14.2   (1.05)   (†)
                                                                                     
Highest degree earned                                                                                    
Less than bachelor's 13   (1.4) 23   (1.6) 33   (2.3) 43 ! (21.5) 40   (2.9) 39   (5.2)   (†) 4.4   (0.42) 6.4   (0.45) 7.3   (0.46) 9.2 ! (4.41) 8.1   (0.58) 8.4   (1.07)   (†)
Bachelor's 189   (5.1) 221   (5.7) 258   (5.8) 259   (11.2) 264   (6.8) 225   (6.7)   (†) 61.4   (0.75) 61.9   (0.90) 57.5   (0.64) 55.5   (2.90) 53.9   (0.95) 48.5   (1.37)   (†)
Master's 92   (3.8) 96   (3.1) 136   (4.5) 138   (6.1) 161   (5.3) 166   (7.5)   (†) 29.8   (0.73) 27.0   (0.71) 30.3   (0.58) 29.5   (1.35) 32.8   (0.84) 35.8   (1.16)   (†)
Education
      specialist3
9   (0.9) 11   (0.9) 14   (1.0) 17   (2.4) 14   (1.3) 23   (2.3)   (†) 3.0   (0.30) 2.9   (0.24) 3.1   (0.19) 3.6   (0.54) 2.8   (0.25) 5.0   (0.48)   (†)
Doctor's 4   (0.7) 6   (0.8) 8   (0.8) 10   (1.2) 12   (1.9) 11   (2.0)   (†) 1.5   (0.23) 1.8   (0.22) 1.8   (0.16) 2.2   (0.26) 2.4   (0.38) 2.3   (0.41)   (†)
                                                                                     
Years of teaching
      experience
                                                                                   
Less than 3 38   (1.4) 47   (1.8) 73   (3.0) 71   (17.5) 72   (4.8) 52   (7.1)   (†) 12.4   (0.44) 13.2   (0.47) 16.3   (0.44) 15.2   (3.50) 14.7   (0.92) 11.2   (1.54)   (†)
3 to 9 111   (3.4) 123   (3.6) 144   (4.1) 162   (7.1) 163   (5.9) 150   (6.3)   (†) 36.1   (0.85) 34.6   (0.67) 32.0   (0.56) 34.6   (1.65) 33.2   (1.05) 32.3   (1.07)   (†)
10 to 20 109   (4.3) 122   (3.9) 137   (4.1) 130   (7.3) 133   (4.8) 147   (7.6)   (†) 35.6   (0.78) 34.4   (0.77) 30.6   (0.54) 27.9   (1.63) 27.1   (0.83) 31.6   (1.38)   (†)
Over 20 49   (2.8) 63   (2.8) 95   (2.8) 105   (7.0) 122   (4.7) 116   (7.2)   (†) 15.8   (0.65) 17.8   (0.73) 21.2   (0.47) 22.4   (1.62) 24.9   (0.88) 24.9   (1.44)   (†)
                                                                                     
Level of instruction4                                                                                    
Elementary 179   (5.6) 225   (4.7) 261   (5.8) 263   (17.5) 258   (6.5) 245   (9.3)   (†) 58.3   (0.92) 63.2   (0.72) 58.1   (0.66) 56.4   (3.06) 52.8   (1.03) 52.8   (1.67)   (†)
Secondary 128   (4.7) 131   (4.0) 188   (6.2) 204   (13.4) 231   (7.1) 219   (9.9)   (†) 41.7   (0.92) 36.8   (0.72) 41.9   (0.66) 43.6   (3.06) 47.2   (1.03) 47.2   (1.67)   (†)
—Not available.
†Not applicable.
!Interpret data with caution. The coefficient of variation (CV) for this estimate is between 30 and 50 percent.
‡Reporting standards not met. Either there are too few cases for a reliable estimate or the coefficient of variation (CV) is 50 percent or greater.
1 Data for years 1987-88 through 1999-2000 are only roughly comparable to data for later years, because the new category of Two or more races was introduced in 2003-04.
2 Includes Pacific Islander for years 1987-88 through 1999-2000.
3 Education specialist degrees or certificates are generally awarded for 1 year's work beyond the master's level. Includes certificate of advanced graduate studies.
4 Teachers were classified as elementary or secondary on the basis of the grades they taught, rather than on the level of the school in which they taught. In general, elementary teachers include those teaching prekindergarten through grade 6 and those teaching multiple grades, with a preponderance of grades taught being kindergarten through grade 6. In general, secondary teachers include those teaching any of grades 7 through 12 and those teaching multiple grades, with a preponderance of grades taught being grades 7 through 12 and usually with no grade taught being lower than grade 5.
NOTE: Excludes prekindergarten teachers. Data are based on a head count of full-time and part-time teachers rather than on the number of full-time-equivalent teachers reported in other tables. Detail may not sum to totals because of rounding and cell suppression. Race categories exclude persons of Hispanic ethnicity.
SOURCE: U.S. Department of Education, National Center for Education Statistics, Schools and Staffing Survey (SASS), "Public School Teacher Data File," 1987-88 through 2011-12; "Private School Teacher Data File," 1987-88 through 2011-12; and "Charter School Teacher Data File," 1999-2000; and National Teacher and Principal Survey (NTPS), “Public School Teacher Data File,” 2015-16. (This table was prepared September 2017.)