Noisy babies/toddlers can be disruptive sometimes. Especially if the play is being done by the smaller, quieter voiced children.
But I do think some schools go over the top.
I remember once there were two performances, one am, one pm. You didn't get to choose which one you saw. The school gave you a ticket for either am or pm randomly.
I had a nursery aged child. [nursery attached to the school]
You would think that I would have been given a ticket for the performance during my childs nursery session.
I was given a ticket for when I would have him with me, he said 'look, its xxxx' when he saw his brother and the dep head came over and made us leave.
Once outside the hall I pointed out the above, said I would have much rather have seen the performance without my 3 yr old and also asked why the adults who were loudly talking weren't asked to leave, she ignored my points and I didn't get to see my 6 yr old in the play.
It really annoyed me!