Often I meet with families, and their children are struggling through high school. These students often are very intelligent but are challenged by executive function deficits. They do their homework, but do not submit it. Finish their exams, but make "silly" mistakes as they often tell me, or do not have time to double check their work. Students with ADHD are eligible for 504 plans, and sometimes if they have other learning challenges, can be eligible for an Individual Education Plan (IEP). Please do not think your child is not eligible because of their intelligence level being too high, this is not true! I really like this site, especially in providing information for high school students. I think their interpretation of high school being like 6 or 7 part time jobs with 6/7 different bosses is a great metaphor for what our students are experiencing. I have several students that go to multiple teacher sites daily, just to get their teacher assignments or announcements. This is not multiple clicks off the school website, but actually different websites with different logins. This can be a nightmare! Extended test times, modified homework or extended submission time, are just a few examples of accommodations. Take a look and see if any of these accommodations would benefit for your child.
http://www.addvance.com/help/teens/high_school.html
http://www.addvance.com/help/teens/high_school.html