Under 5s probably would not be excluded from some or all of schools' nativity plays etc if some parents were better at getting their small children to behave and/or taking them out, if they were being disruptive.
For all those saying 'it's not RADA' - well, no it isn't - but it IS very special to the children involved, and they and their teachers have worked very hard to make the play or performance the best they can - and when smaller children are running around, shouting, crying, generally disrupting the whole event, it spoils it for the children taking part - and I am sorry, but to me, their feelings matter most!!
If your child has worked hard to learn their part of the play, and then it's disrupted by a toddler whose parents can't or won't make them behave - and your child is put off their performance - is that OK? I don't think so.
I have gone to primary school nativity plays with smaller siblings of the child involved in tow - and I made sure that my boys behaved themselves, didn't make noise - and if they had, I made sure I was near enough an exit to whip them out quick-smart, and would have done so!
Yes, the nativity is a family thing, but is the toddler who is screaming their head off enjoying it? Appreciating it? What about the one who is treating the hall like a playground? I doubt they are really taking in what is going on on the stage. So for the sake of these children, the ones who have worked hard on their play, and their parents, must have the whole thing ruined? NO!
I think that a fair compromise is to do a performance where smaller children are welcome - and then the teachers can prime the performers to be aware that there will be lots of noise, so they can cope better - and a performance where no under 5s are allowed, so parents can enjoy the play.
I am utterly baffled that someone can read a note that says 'No under5s - due to space', but can argue that that doesn't mean 'No under 5s'!! Nativity - the second part of the sentence EXPLAINS the rule, it does not change it. I have no doubt you were embarrassed to be asked to leave the hall - but it was your own fault, no-one else's.