I was diagnosed a month before my 19th birthday.  I graduated HS in the top 3rd of my class and got an associates degree with a 3.875 GPA.  My brother, who does not have CAH, did quite a bit worse than me until he was in HS and college.  The academic abilities will probably have more to do with the parents’ education level and if there is a history of learning disabilities present in the family.  This child may be your best or worst student, but I believe in most cases CAH has little to do with academic abilities.