Private school is a private financial transaction so it depends on the details. If there is no contract, or the school and parent signed a contract that allows the school to kick junior out at their discretion then that is that. If there is a contract that promises to educate junior for a certain lenght of time and the ability to eject a student is ill defined then mom may have a case that the school violated it's contract and she was damaged by having to find another school on short notice.
Of course and she should continue to post about them, as is her right too.