Welcome to Scuba Board.
A couple of things you might want to try to help you ease into the process. Start out by only letting a little bit in at first and work your way up to being able to remove, replace and clear the mask. A neat trick is to slightly lift the skirt just above one corner of your upper lip away from your face using the thumb and forefinger. This way, it is easy to control the level of water entering the mask.
Tips I learned from my students:
Try closing your eyes. I don't know why, but this seemed to help some of my students.
My 10 year old son claimed he perfected his technique by filling his mask up with water, lifting his head above the water and blew through his nose. He said this allowed him to see just how much air he required to clear the mask.
Good luck in your class,
c