There are different answers so I'm in doubt which the right answer is.
SoothingDave is a speaker of American English; I am a speaker of British English. There are areas of usage in which the two varieties differ; this is one of them. If the variety you are learning is BrE, stick with my answer; if it's AmE, stick with Dave's.
In any case, context will normally make the difference clear, even if you choose a preposition that sounds a little strange to your listener. If you are worried about this, change the structure: 'Mr Smith taught me French'; 'Charlie Smith was in my French class at college'.