Settling into the school routine is tough enough. When you are a newly separated family, settling in can be - and usually is - even tougher. You have new homes, new bus routes, new morning and bedtime routines - we could go on and on. This, on top of new teachers, new classmates and new school parents to deal with, many of them judgey.
If you are sharing your kids in a court order, there will inevitably be issues. This does not mean the other parent will purposefully hurt you -- though that could, and sometimes does, happen - it means both of you are learning the ins and outs of a two-household situation and there will be differences on opinion.