The only music theory I did at school was in primary school and my first year of high school where it was compulsory.
When I was in my final year of high-school, though, I sat the music exam to leave open the option for me to do a music degree at University.
I didn't actually attend any music classes, though, I just read books on my own so I think by most people's definition, I got to that level through self-learning.