Management Problem

My main management problem this semester has to do with managing my time at school and two jobs. Since the semester began I had to cut hours in my monday through friday job and my boss has not been happy. Ever since I work less hours my boss has been more demanding and at times making me late for class when she asks me to do something last minute. It is very difficult for me to make it to my first class on the scheduled time since my boss keeps wanting my to do this when she knows I have to leave.