These tests are given on Saturday mornings, 7 times each year. In spring, summer, and early fall, Saturdays are baseball days. Look at the schedules for both SAT and ACT, and figure out when your son will not have a baseball conflict - there will probably be only a few dates, in November-February. Do them both this winter, then focus on the one he does better, to take again junior year. By that time you may have a better idea of who is recruiting him, what score they will want, and whether he needs extra work to get that score.