I also recommend the P.E.T.E. and as Wynton says, be patient, don't rush to get results, going to fast (with the P.E.T.E. and trying to extend your range with your centred(ish) placement) will only damage your chops. If you go down to the gym for the first time you don't try and bench press 350lb, you will damage the muscles and in the end take you longer to lift the weight than if you worked through a well thought out and planned program. I also think your teacher is playing with fire. (play on the side until you want to go pro! then you will have to change and have a great set back just when you should be making strides forward). Build strength and consistency and range will come, most music for the trumpet is from low G to high C/D above that is in the realm of lead guys and piccolo tot players.