Well... he is at a good time to make dinner...
It may be hard, but how bout turning this into a lesson about the food system? Like, learning where your food came from? I butchered birds when I was young and think it is a good thing to be able to teach the younger people of today that the shrink wrapped meats in the store came from a live animal. Maybe it can be part of the classroom project extending on to the circle of life? It really is up to you. Butchering isn't that hard of a job. The hardest part is the actual taking of the life. The rest is cake compared to that. If you are interested, you can search though the meat bird section for how people have done it. Just don't forget to age him in the fridge for 2 days or so, so the meat would be tender. Fresh chicken does taste much better and is not mushy like store meat.
But on a restricted diet, he looks good for his age and might be able to make it to a full year, or even longer before he gives out. Just have to be very pro active at getting him to move. Having coop mates that are not boilers helps out with that respect. But then again, he may crow in that year which means you'll have to find him a new home.
I personally would make dinner out of him, but not everyone will agree to that.