I sat in on my son's HTE course, and the instructor talked me into actually taking the exam, since the HTE Card would be beneficial to have if I ever wanted to hunt in some other state that require one.
Anyhow, there was a lad that visibly had some type of learning issues. He sat directly in front of us, and there was absolutely no way this youngster was going to pass the test on his own. The instructor(s) realized this, and one actually sat with him when it came test time, and coached him into the answers... Kinda by way of process elimination ? Soooooo, I believe contacting the PGC prior to taking your son would be beneficial, and more than likely, some sort of guidance can be arranged at test time ? Now that's just me basing things on what I witnessed.
Good Luck. Wish you guys well.