More detailed information on 2009 ninthgraders produced by the National Center for Education Statistics (NCES) using the High School Longitudinal Study of 2009 can be found in the following publications:
Data Point—Parent and Student Expectations of Highest Education Level (NCES 2019-015). https://nces.ed.gov/pubs2019/2019015.pdf
First Look—High School Longitudinal Study of 2009 (HSLS:09) Second Follow–Up: A First Look at Fall 2009 Ninth-Graders in 2016 (NCES 2018-139). https://nces.ed.gov/pubs2018/2018139.pdf
Stats in Brief—Ninth-Graders’ Mathematics Coursetaking, Motivations, and Educational Plans (NCES 2015-990). https://nces.ed.gov/pubs2015/2015990.pdf
Stats in Brief—What High Schoolers and Their Parents Know About Public 4-Year Tuition and Fees in Their State (NCES 2019-404). https://nces.ed.gov/pubs2019/2019404.pdf