Typical bank MrsC. Sounds to me that she is pulling thee 'ole "I am in charge, I say no" card. Also, I've seen supervisors NOT want our tellers to go to school, for fear of losing them.
Too bad for her, cause she'll lose you in a NY minute. Schooling is more important than working for someone who doesn't care about you and your education, she needs to know that she's toying with your livelihood now....ain't nobody qualified to do that.
Put your foot down! I'll back ya up.