"I remember talking to dd1's head teacher when she was in year 3 (dd1, not the HT ) and she said that it's at that age that the girls in particular can start falling in and out of friendships, then it can start to get nasty, ganging up on others etc".
Unfortunately I agree with this, one of DD's best friend's has turned on her and had her in tears for 2 days running by having a go at her and telling lies about her, I had to inform the school in the end and the girls in the class were given a talking to about snitching and making up lies about others. I did wonder if because its a big jump from infants to juniors and some children are unsettled, and also because they are at the age now where friendships are established and I have noticed that now there seems to be groups of 3's and thats why friends are falling out with the 2's company 3's a crowd scenarios.