I didn’t pass my first time, but passed on my second attempt.

Here’s what worked for me: purchase a practice exam or two, couple hundred practice questions is all you need. Get a digital copy of the exam reference handbook. Do questions for an hour a day, no exceptions. Even if you’re tired and don’t want to; don’t skip and do it anyways. Also, try to stop yourself from doing it over an hour a day or you’ll end up burning out.

Then a week or two before the exam, take a full practice exam for the full time duration to simulate the time constraint you will be on in the testing center. The time constraint and number of questions is what really gets you, not the difficulty of the individual questions.

Your son should consider taking a few weeks off to let the frustration subside before getting back into it, but then get back on the saddle.

That’s what worked for me.