I found this old PS Grand Turismo disk (no idea where it came from) put it in and I've been playing this game for aboyt 4 hours a night for the last three weeks and can not get a class A license.
The one that's always gotten me was that A-License test at Trial Mountain with the R33 Skyline. That was always a tough race. Thankfully in future GTs, this test would be a bit easier. Just keep at it. Keep fighting hard, soldier!
I always used to struggle with A-3, the test with Mazda RX-7. I reckon if you can pass taht one, you should pass the others. International A will be much harder though, but you'll gain some skill in the races which the A Licence allows you to do once you obtain it.
Good Luck