Congratulations to you on your son’s graduation. Your son can definitely re-take the SAT after high school, whether it’s this coming fall or further down the road.
He just needs to register at the College Board Web site as he has done already, and when he’s asked to choose a test center, he can select his old high school if he wants to (and if it’s an option) or he can pick any other test center that is convenient.
Although the test is primarily taken by high school students, there are other young adults who take it as well … and even some not-so-youngadults.
However, if your son is planning to be in school in the fall (e.g., in a community college), he might want to postpone the re-test until he has taken additional math and English classes. This could help him boost his SAT scores the next time around. He would also be wise to prepare for the test using practice books or online materials. Prep courses can be expensive, but books and online study aids are usually fairly inexpensive or even free, especially if you buy them used. In fact, your son probably has friends who would be delighted to part with their used SAT prep stuff for free with the hope that they never have to even think about those tests again!