My dc go to a nice little rural school with 32 kids.
My eldest ds1 has just moved from the junior class up to the big class.
DS has always looked older and seemed older than his peers. The headteacher writes this in every report we have had from school. Thats how much it stands out. Although im not sure why she keeps remarking on it.
Ds had always played with the boy in class year above him. He was the only boy in that yr and him and my son got on well. When he moved up to big class last year he didnt want to continue playing with ds because he was trying to fit in with older class mates. There was a bit off a problem, i wasnt told until parents evening but apparently there had been a problem big enough that parents had been called etc but my ds not directly involved. Clear as mud i know but I only got this info and was told its now 'fine'. When i asked my ds about it he was very defensive of this boy. When i asked if he didnt want to play with him anymore he said 'X would never do that'. Ds kind of idolised this boy as he is very sporty etc.
Ds went on to be friends with a boy in his own yr, who is the cousin of this boy (small school lots of them related or very local) Last year all was fine.
Now ds tells me since they have gone up to big class the older boy has taken the cousin under his wing and takes him off to play 'secret' games that ds cant play.
I was at school today helping and i can see how much my ds stands out. He isnt one of the little ones that the big ones look out for but he isnt actually 'old' enough for them to want to be his friend. I feel so sad for him when he comes home and says 'i used to be popular but now no one likes me. 
I feel like i want to move him to a big school where he will have a bigger pool of people in which to find a friend. When there is a problem in a little school there is often no where to go. You cant get away ikwim.
I dont however want to teach my son the if there is a problem you should run away.
Sorry so long... tea and biscuits on me.