Sorry, a bit of a smart alec remark... but isn't that what No Child Left Behind is for?
Serious answer: One of my best friends as a teenager was... well... simply put... not too bright. She'd work her toosh off, but still pulled a C average at her very best. She got into college, despite her lack of academic prowess, and lasted about a year before she flunked out. Now, it wasn't that she wasn't trying, or going about it properly, she just didn't do well in academic situations, no matter now much effort was thrown at it.
Since then, she was able to get into a slightly different educational program and now is a teacher's aide in an elementary school. Her tenacity and personality do a lot more for her than what her lack of academic ability takes away. She's happy, successful, and due to her own experiences is very compassionate to the kids who just aren't good in school.