My year 6 ds was recently corralled into doing a day of 'fun' PE activities at the local secondary school. He wasn't keen on the idea. I rang up to remind the school that he wasn't going to be attending this secondary school (when ds said only some of the class were taking part I'd assumed it was a transition day thing).
Teacher sheepishly said that, um, actually it wasn't that, ds had been selected as part of a group of 'children who aren't very keen on PE lessons', to try some new, exciting stuff.
Oh well great then, bring it on, I said (very aware that ds is a bit of a nerdy chubster, would love him to enjoy sport more).
I explained this to ds, putting a positive spin on it.
'Mum', said ds, wearily, 'It's for Fat Slackers. I already knew that. Fine. If I must.'
So I'm a tad sceptical about compulsary PE afterschool for the Fat Slackers, given the lack of enthusiasm for an intervention that involved a whole day out of school & a chance to use super-duper secondary facilities.
Ds likes swimming, & martial arts, & is pretty good at both. He & I have swum 1km together most days since holidays started & are both becoming more svelte.
Kids who don't like school PE are really, really unlikely to be cheerfully engaged with more of the same that impinges on their free time...nice idea OP, but crap kidology!