Appropriate punishment for 8 year old

[MrsSnape]

Was just walking home from school and DS and his friends were walking far ahead of us.

Anyway in the distance I saw a bloke walk up to them, grab DS's friends' arm and push him and start shouting at them.

I obviously rushed up and caught the gist of it ... the bloke was one of the boy's fathers and had just seen DS and his other friend push his son over and kick and punch him. (from a distance it looked like they were playing, they often 'play' like this).

It was only when I got closer that I realised DS and his friend had ganged up on the other one.

I apologised to the father (who was nicer to me than I expected him to be) and promised I would punish DS.

So, how do I punish him? I hate bullying. I want it stopped now.

Written apology to the boy in question?

Written letter of apologyis a good start, but doesn't sound enough to me. Maybe ban ds from something he loves for a period of time?

Appology and a ban from screens for a period?

I would also be tempted to contact the school and let them know this has gone on so they can monitor the situation in school (although I would not tell ds of that unless you think it could be a tool to make him realise how seriously this behaviour is taken).

BTW, well done for dealing with it, IME bullying at this age is met by "Not my Johnny, he would never..."

Message withdrawn

I have found that grounding my 8 year old DS works amazingly. It only occured to me a little while ago that the only thing he loves doing is playing football outside with his friends so I decided that it would be his punishment to be banned from going outside, the length of time dependent on what he did. He can see his friends from his bedroom window playing football on the grass so it really is a punishment!
Is there anyway you could use grounding as a punishment?