My late August born DS has had a surprisingly good reception year. He's been happy, made friends and seemed to be progressing reasonably well. However in the last few weeks it's all started going a bit wrong. There's a particular boy who's at the older end of the year, is much bigger and more assertive. According to my DS he keeps bossing him around, making him play games he doesn't want to play, calling him a baby etc. None of it sounds terrible but it's clearly really upset him because now when we see the boy outside of school DS hides and gets very physically stressed/upset. I've told the teacher who's lovely and very sensible. She said that although she can imagine what I'm describing based on their personalities she hasn't seen anything particularly untoward. She said they would keep a much closer eye on it over the next week and then we could talk about it again. What can I say to him or teach him to help him learn to deal with this kind of behaviour?