sports camp?
I really don't think it's mean to expect a new secondary age child to entertain himself in 1-2hr chunks through a day.
or the really mean approach- after all he IS old enough to entertain himself assuming no SN etc - right if you can't find things to do I will find them for you:
Firstly Take all your clothes out of the closet and drawers and check they all fit and you are happy to wear them. Fold/hang/put away tidily.
Then you can take the out grown clothes to the charity shop- it's here- have a map and walk or get the number X bus ....
Then sort all your books/school paperwork- again chuck out the duff stuff and put the rest away neatly...
and when all that is done, and I have done my days work we can go out for a meal/take a picnic to the park etc
Next day finish systematic tidying, change bed, put sheets in wash, hang em out, hoover floor etc
Again rewarded by real quality Mum time in the evening- as he will have allowed you to work during the day.
I could keep an 11yr old gainfully employed about the house/garden for ages..... not in an " I'll send you sweeping chimneys" way but in a " these are jobs that need doing and skills you need to learn. If you do them I shall have free time to spend with you in return" way.
He might like doing chores and that's great, but if not I bet you'll find him suddenly distracted by the lego box he forgot was under the bed, or similar!