New jacket

Ah, I can see that could be a problem. 

Even so, it might be useful to find out why he likes the old one, and whether anything would entice him to wear something else. Have you thought of offering him hard cash or a clothes voucher in exchange for the old jacket?

Or could you have a quiet word with one of his teachers? 

Thanks. Our problem is that he is about to start secondary school and wearing a too small jacket he is judging setting himself up to be picked on. 

Personally I would not worry too much. He will eventually grow too big to squeeze into it, and most kids I know will do the exact opposite if you nag them!

Have you tried asking him out of curiosity what he particularly likes about the jacket? Is it the tightness, or is he attached to the feel or the smell or the familiarity of it? 

I was on a course recently on 'influencing skills' and one of the suggestions was that the main question anyone has to ask if you are trying to get someone else to do something, was "what would it take for you to do X / give me X?"

My parents would have just shrugged and said "so what, don't complain when you get cold then"!