There are several things Sean should do:
1. Talk with his teacher. Sean should see if his teacher can explain where he went wrong on the homework assignment to help him understand how to fix his mistakes.
2. Sean should study in a way that helps him retain the material: this includes repetition of the vocabulary and ideas, re-writing notes to get a physical to mental connection between the information and his brain, and possibly making up rhymes/songs/mnemonic devices to help bring new ways of remembering the material.
