This study followed 539 boys from the Pittsburgh ADHD Longitudinal Study. Of them, 326 had been diagnosed with ADHD as children, and 213 were similar boys without ADHD. Researchers looked at how they did in high school, in and after grades 9 through 12.
The boys with ADHD did worse across the board. Their grade point average was lower by about 5 to 9 points on a 100-point scale, which put the ADHD group near a C-minus and the comparison group near a B-minus or C-plus. They finished and turned in fewer of their assignments (64% of the time versus 83%). Fewer of them were seen as working up to their potential (30% versus 61%). They were absent more often (about 17 days versus 10) and late more often. They failed more of their main academic courses (7.5% versus 1.7%). They were also far more likely to leave school. By the end of 12th grade, 85.9% of the ADHD group were still enrolled, compared with 98.6% of the other boys.
The researchers note some limits. Every boy with ADHD had attended a childhood summer treatment program, so its effect could not be separated out. Grade point average is also a rough measure that differs between schools, and there was no data on learning disabilities.
Source: Kent K, Pelham W, Molina B, et al.. The Academic Experience of Male High School Students with ADHD. Journal of Abnormal Child Psychology (2010). doi:10.1007/s10802-010-9472-4