OK thanks @chemmchimney !
When you take subject tests (grade level) really depends on your course selection. Some kids take tests at the end of 9th or 10th grade if they are ready. Math 2 can be taken after pre-cal, sciences after regular or AP, history after appropriate class, etc. But it is true that not all classes line up exactly with subject test. Students can talk to the teachers and ask their opinion. DS has been taking them in May since June is usually right when he gets home.