Op - my ds is 13, in year 8.
He gets FSM, so he is entitled to a main dish plus desert everyday.
Last year, when he started secondary, he also started earning money walking a friend's dog, so he had money in his pocket, and a whole canteen to choose from and a poundland on the way home from school.
he went a little mad. He shunned the nice roast chicken dinner and desert and bought pizza or chips every day. After school they went to poundland or the chip shop and stuffed crap. He guzzled can after can of coke and fanta.
He came home to nice home cooked balanced healthy meal, and wasn't interested as he was full of chips and fizzy drinks.
He has always been very slim, but I could see he was starting to put on weight.
I talked to him about healthy eating, and he said yeah, yeah, and didn't change his behaviour at all.
Then this year, he decided to get fitter, and after a talk at school became interested in how much sugar there is in stuff. I notice that although he still eats pizza for lunch every day, he has stopped visiting the chip shop, and eats much less chocolate, he chooses not to drink fizzy drinks everyday too.
I think it is quite normal for kids starting secondary to go a bit mad over being able to choose from the canteen, being free and out from under parents or primary school dinner ladies scrutiny. It does balance after a while, if you let it.
I totally get that he has food problems and you want him to loose weight, I get the frustration and distress with stealing, I get that you want a daily limit on the card, but you also have to get that he is growing up, and moving out from your control, and you need to find a new way of approaching this.