Average score is higher than U.S. average score at the .05 level of statistical significance.

Average score is lower than U.S. average score at the .05 level of statistical significance.

¹ National Defined Population covers 90 to 95 percent of the National Target Population.

² Met guidelines for sample participation rates only after replacement schools were included.

³ The number in parentheses indicates years of school not grade in schooling.

⁴ Nearly satisfied guidelines for sample participation rates after replacement schools were included.

⁵ National Target Population does not include all of the International Target Population.

⁶ National Defined Population covers less than 90 percent of the National Target Population (but at least 77 percent).

⁷ Reservations about reliability because the percentage of students with achievement too low for estimation exceeds 15 percent but does not exceed 25 percent.

⁸ Did not satisfy guidelines for sample participation rates.

NOTE: Education systems are ordered by 2015 average score in reasoning. Education systems that are not countries are designated by the appended three-letter international abbreviation for their country. Participants that did not administer TIMSS at the target grade are not shown; see the international report for their results. U.S. state data are based on public school students only. The TIMSS scale centerpoint is set at 500 points and represents the mean of the overall achievement distribution in 1995. The TIMSS scale is the same in each administration; thus, a value of 500 in 2015 equals 500 in 1995. Standard error is abbreviated as s.e. For TIMSS 2015, Norway revised its assessed population to students in their 5th and 9th years of schooling to obtain better comparisons with Sweden and Finland. However, in previous TIMSS cycles Norway assessed students in their 4th and 8th years of schooling, which were defined as 4th and 8th grades but have been redefined as 3rd and 7th grades because year 1 in Norway is now considered the equivalent of a year of kindergarten. To maintain trend with previous TIMSS cycles, in 2015 Norway also collected data from students in their 4th and 8th years of schooling, which is used in trend tables.

SOURCE: International Association for the Evaluation of Educational Achievement (IEA), Trends in International Mathematics and Science Study (TIMSS), 2015.