My Manager Is An Imbecile 😐

I, earlier this year, told my manager that I couldn't work certain hours or work late due to me being in school and I assumed we were on the same page... Until today. He has me on the schedule late tomorrow and I have an exam on Thursday. I told him this and he's like "I don't care about what you have going on in your personal life" and that... Pissed me off because college is my main priority and he knows this.