Safeguarding training includes issues around domestic abuse, and it is mandatory. In my experience, teachers and schools are very careful indeed to maintain a non-judgemental attitude towards parents in this kind of situation. The biggest issue is that many parents use the child/ children as weapons in their dispute, and they often choose the school as their battleground.
I have experienced parents screaming abuse at one another across the hall at a parents’ evening, lying brazenly about aspects of their children’s circumstances, withholding payment of independent school fees to blackmail an ex over a divorce settlement, and breaking into school and threatening to beat up a teacher in the staff room. I’ve had aggressive phone calls and threatening emails from both parents of a student, each intent of recounting the details of their relationship to try and persuade me to take sides.
If I’ve learnt one thing over the years, it is that both parties to domestic disputes see themselves as victim, and schools have to go to extraordinary lengths to remain impartial, while still caring, teaching and safeguarding the child or children involved. It think it unlikely that a teacher would ‘favour’ one parent, but it is probable that both parents feel that the school should take their side.