NCAA requires a progression in various history, English and math classes. Different high schools have different curriculum. So its not just a matter of looking at transcripts. Does not matter what a course is named. You need to dig deeper and look at course content, at all three high schools. Did he take same math class in different schools with different names. Did he progress in course complexity and content. Or did he stay at remedial or beginner level. When a student attends many schools, process is longer, layered and more complicated, and it is more likely for something to trip up eligibility. One class that is ruled duplicative is enough.