I teach at the same school my ds1 goes to. I was there for a year before he started in Reception. He was quite mature about it, he felt "special" and it did help his transition from nursery to school as he knew he could see his mummy in the day when other children couldn't.
I told him that he should call me Mrs InTheseShoes when he was with the whole class (e.g. when I entered the classroom and said "good morning Reception/or whatever" but that he could do it with a big wink to me - he liked that and does it to this day (he is Y2 now) but he calls me Mummy any other time.
Obviously he is still quite young at the mo, and really seems to like it. In some ways it is harder for me as I know I am tougher on his behaviour if I see him, and also want to interfere in stuff and have to restrain myself. On the other hand, his teacher sends him on messages to my class that are required and he likes that, as do I. I have always insisted that I have a proper Parents Night appointment (manage my appointments to fit in with my one with his teacher) and I complete every letter/reply slip etc as his mum and not a teacher. He bumped his head badly once, and I was so glad that I could be on the scene immediately.
However, I did have to take his class a couple of times when his teacher was teaching PE for me when I was heavily pregnant with ds2 and I didn't like that - he showed off a bit and I was tougher on him than on others - I would not recommend teaching your child unless absolutely necessary (and as I could not perform a roly poly then it was in that case).
I am in a different key stage this year than ds1, and I find I barely see him; you might find that to be the case too at secondary school. Of course, the "skitting" from other pupils might be more at secondary, could you work out a pre-prepared "line" for your ds to take on that one? Try to anticipate the things he might have to deal with and explain that you're not bothered about whether the kids slag you off or not? (I am assuming that this is the kind of thing you are bothered about here)
I do think the benefits outweigh the negatives - just the thought that you are there immediately in any crisis is plus point enough.
Hope all goes well for you - best of luck!