My 4 year old has recently started biting, which at his age seems ridiculous and I'm gutted about it. He has bitten in school 4 times over the past 3 weeks, we went in and had a meeting with the head and bought "teeth are not for biting" book, we read it and we've spoken about using our words, how violence is never ok. He has been good at school this week, I picked him up today and his teacher said it seems to of sunk in and he was good as gold, I took him to meet a friend at softplay as a treat for being so good and within 10 minutes he had bitten another child. We left instantly, I had to physically drag him out screaming, he was hysterical in the car. When he calmed down he was begging me to take him back, I said no, asked if he knew why we left, he said because he bit someone, I asked why did he bite? He said the boy was holding his leg and he wanted him to go away. I said and what do we do next time someone is doing something and you don't like it? He said use our words, not bite. He said sorry. But I'm just gutted to be honest, why would this start now? He's 4, he has good speech, he can communicate and he understands it's wrong. Why is it happening? How do I make this stop? I know it's normal at his age, but what do I do?