I need job advice

I’m gonna try to make this as short as possible but it’ll prob end up being long.

I work in a special ed classroom. It has become a hostile work environment for me because of the teacher in the room. I won’t go into too much detail but she constantly harasses and verbally attacks me. I’ve had numerous emotional breakdowns to administration about this and they have been very supportive. They see the issues. My co worker has also gone to them about issues with her and true teacher of the room. After meeting with admin multiple times, I have always agreed to try to continue to deal with it and try to make it work and see if things get better. If they do, it’s for a very short period of time, and then it’s right back to how it was or worse. This last time I went to admin was probably about the 5th or 6th time. They told me they needed time to brainstorm so I said okay. They were on my side. I took it upon myself to e-mail HR and explain the situation, requesting a transfer to another school. HR emailed me back and told me they’d talk to the admin at a different school and get back to me. A week went by and in the meantime I also interviewed at a completely different company, which is a huge pay increase, way better benefits, just all around better.

So I requested a transfer and then interviewed elsewhere right. Finally I hear back literally this week (on Monday) that I’ll be transferring to a different school on this coming Monday. THEN today I get the call back for the job offer from the other company that I really, really want. Of course I accepted. So tomorrow (Friday) is my last day at current school, Monday I’m to start at a different school and towards the end of March is when I’m able to start with the new company (that’s when the next orientation class is) WHAT DO I DO?

I feel like a total ass transferring to a new school that needed a position filled, only to work there for a month and then say “sorry you’re gonna have to replace me now here’s my 3 week notice.” But my current school is already expecting my last day as tomorrow. I can’t afford to just not work for a month until the new job starts. Should I go to the admin at my current school and explain the situation? I don’t know if they’d say okay you can just stay here until you leave (and then I’d still have to deal with the hostile work environment for a little longer) or do I just really be the person who transfers and then tells them a week or two later about my notice to leave. I know either way it doesn’t look very good, but I can’t help the timing.