I was a TA at the primary school my ds's attended and there were several others over the years who also had dc at the school. It can be very convenient provided there nothing happens that can put you, in your parent role, in conflict with the school. In theory, this should still not be a problem but it can be.
If there's something you need to know it is handy to be able to ask a teacher in the staff room but if I needed to do this, I'd always preface it with "Can I just ask you something as a parent..." and make sure I didn't do it very often. If it was something big or confidential, I'd request a meeting after school just like any other parent and expected them to do the same.
However, sometimes things got tricky. These are some of the things that happened to some of us during our time there:
- a senior member of staff started talking to a TA mother in the staff room about some confidential information regarding her child in full view and hearing of everyone else, whereas a "normal" parent would have been seen in separate room, been forewarned about the issue and would have had the chance to have the other parent present.
- a TA was taken to task about her sick child's attendance by the head teacher in the corridor of the school with pupils walking past and able to hear everything.
- staff talking casually about a TAs child's behaviour and forgetting that the parent/TA was in the staff room and could overhear it and then suddenly remembering and going silent.
Also, what do you do if you are unhappy with something that is happening in your child's class? You may have had quite a friendly relationship with the teacher but if you want to query something as a parent e.g. how an incident of bullying involving your child was handled, the relationship may become strained.
I wouldn't say don't do it and obviously I did, but it wasn't always easy. We weren't allowed to be based in the class our dc were in and this helped. However, although I don't work there now, I know that with cutbacks, TAs work across a number of different classes in my old school so may come into contact with their dc's