Hmm, using the C button always worked for me...
If your timing is slow, try this. As soon as the school is shown press A as fast as you can. You will most likely change the teacher.
If you want Fashion skills fast, feed the following foods:
All skills +1
All skills +2
Cupcakes are Young Memetchi and Memetchi's favorite food, so you can get eaisy happy hearts and Fashion skills!