Ds is in year 3 and has had glue ear from a baby; he's on his third set of grommets, one is out though and the other coming out.
It does effect behaviour, however I don't think that is generally known by teachers.
Saying "he may have glue ear and that can effect his behaviour" doesn't necessarily help a teacher who has 29 other children and doesn't personally know your ds.
A lot of children are angels for the first couple of weeks, and then it sinks in that school is more permanent, and they start getting tired, and they start playing up, so blaming the teacher for not noticing is not really fair.
With ds I am always informing the teacher, even now, any changes. Ds went back to school after illness on Tuesday and I spoke to the teacher and said that his right ear is totally blocked and probably will stay that way until Spring. I have told her that he may switch off into his own little world, particularly towards the end of the day when he's tired, he may need to look at her to lip read, he may try and guess what he should be doing, so not doing what he's meant to may be not hearing rather than naughtiness, and that if there's a lot of background noise he will struggle as it gets painful for him.
When he has the next ENT appointment I will let her know how his hearing is. If I notice change, I will let her know.
In reception the teachers got to know him so well they could predict an ear infection by his behaviour. BUT they had to get to know him first. It wasn't a case of automatically knowing, they had to see the correlation because ds is perfectly capable of being naughty on his own. 
What they did do in reception was a behaviour book where they wrote several times a day good/bad things. it helped to see a pattern. With him he struggled with a lot of background noise so lunch/break were difficult. And tiredness-Thursday afternoon was particularly bad. They couldn't, and I wouldn't have asked, spare an adult to follow him round to remove triggers, however with the behaviour book they pointed out a couple of things that were triggers and could keep an eye out-not entirely eliminate- for them.
And I'd request an early appointment with ENT (ours will bump you up for a cancelation in such circumstances) and explain that it's effecting him at school.