#1 is not correct, because there is a specific time he started to teach. #2 is perfect English. You could also say 'has been teaching' with no difference in meaning.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
AnonymousIs (1) natural English?No.
AnonymousBut sometimes I do stumble upon the 'has started + since' combination as shown here . Are these examples any different from (1)?Are the examples you stumbled on different from (1)?