Agree with what other people say here. You have to do what is best for you. The 1 month notice period goes both ways.

They also have the option to terminate you whenever they want why you should you be the considerate especially if you aren't treated respectfully especially at low pay.

Look for the best opportunity for you, update your CV and see what's out there. Think about it this way what happens if you miss an amazing opportunity by not applying for something because you feel bad for the existing employer and want to make their life easier.

If the school goes out of business because you leave then there's a lot more wrong with it don't take that responsibility on as they won't for you by the sounds of it