He can call his ED and EA schools and ask if they will accept a December SAT (or ACT) score.
Definitely he should download some old exams and try a timed test for both the SAT and ACT to see which he likes better. Make sure they are OFFICIAL tests (available online) and make sure he takes each section timed. He can do this multiple times (with different tests) and review the questions he got wrong to help improve his scores, if he is motivated to do so.
Good luck to him!