As TheSessler already mentioned, it's not like they had a lot of options. And I'm sure Yoda taught him much more than that. He taught him how to control himself most importantly, how to channel himself into using the force in a productive way.
And I'm sure Anakin was "fully" trained before 12 years was up. He fell because he was far too weak. Luke had less training but was stronger and managed to overcome the darkside of the force. Did you miss the whole point of the movies? (j/k )