Ah, yes... aural theory... bane of music majors everywhere.
As a former music major myself (Bachelor of Church Music, 2003) I can say that aural theory was by far the least looked forward to class among the music students, even more so than "regular" theory because at least with the regular theory it is down in black & white in front of you. Aurual is just floating out there in the air and in your ears. (For those that don't know, Aural refers to sound, so Aural theory is where music student learn to recognize and repeat or write down pitches, intervals, chords, melodies, etc. just by listening to someone playing something.)
I honestly have to say that, to me, aural theory skills are mostly a matter of either you have it or you don't. Not that people who don't have a good ear can't be a good musician, it just makes certain things more difficult. But most of the people who have a good ear seem to have always had a good ear. For instance, you will notice early on that some children can carry a tune better than others because they can hear everything better musically speaking, and that ability usually carries on into adulthood. Some people are kind of in the middle and can improve with practice and training. Others just plain don't have a good ear for such things and couldn't carry a tune in a bucket, so to speak.
I wouldn't want to discourage your son, but aural theory is not easy for most music students, much less those who struggle with it. Of the dozens of music students I was around in my time in college I can say that there were only a very few of us who didn't worry about aural theory and stress out about it.
What is your son's instrument / voice?
As for ways to help, I am a visual learner and always tried to visualize the music as though it was a written sheet of music in front of me (which is, of course, the whole point of aural theory). The more you can recognize what sounds certain intervals and chords create, the easier it will be to visualize them in your head when hearing them. That means, the best way I found was to have music in front of me that I could look at, then listen to what it sounds like so that your brain can put 2 + 2 together that interval A sounds like this. Interval B sounds like that. Chord A sounds like this, etc. etc.
And I've never met anyone who "learned" perfect pitch. I have a good ear, but nowhere near perfect pitch. A very well trained person that already has a good ear can learn relative pitch or near-perfect pitch, but I have never met someone who at one point didn't have perfect pitch and then suddenly learned it. The handful of people I know with pefect pitch seem to have always had it whether they knew it or not, but it wasn't a learned skill.
