Alternatively, MIT assesses each class individually; its math department won't accept credit for math classes taken anywhere else:
This is not strictly true - I transferred from UC Berkeley to MIT, and my math classes did mostly transfer (although they made me take Differential Equations over again, but I probably could have gotten out of that if I hadn't waited until the last possible second to submit my transfer credit application). They won't give credit for dual-enrollment classes (although they will give placement after testing), but they will give transfer credit for university classes of adequate quality if they were not taken during high school. I know that the question was about dual-enrollment classes, but I didn't want anyone to be confused.
