The same thing happened with my school as Frostguard, both choosing to go camp or not go resulted in the "mandatory" completion of the booklet. The camp mostly aims to bring the grade "closer" together so those who didn't go had their booklets checked more rigorously while those who went just threw their booklets away. The work in the booklet was very "explicit" and boys and girls were separated, you get the idea. The certificate is pretty much useless, I didn't even get one, lol.
Food was simple and was limited and consisted of mainly baked beans, powdered eggs, toast and spaghetti (all canned) and lunch was slightly better with things like hot dogs and burgers but overall, you would be better off eating instant noodles for the duration of camp (don't do this). The beds were okay but because of the smell of feet and the sound of snoring, I got 2 hours of sleep for the entire duration of camp.
Some activities required to jump into dirty water and there was this mud course we had to do. In contrast, some activities like the windmill, rock climbing and the flying fox were great experiences and others required a great deal of teamwork which I was dubious about first but once I got into it it became surprisingly rewarding. Although we were separated into groups not of our own choosing, everyone was able to at least talk to each other once in a while.
Overall, despite these fun but not so clean times, I don't think it was worth the $300. I doubt they will do anything to you if you don't go but there won't be much to do at school either. It might be another story though if you wag all together, they'll definitely realise something is up if your absent without much of a reason and will more likely cause a problem than not going camp.Overall, despite these fun but not so clean times, I don't think it was worth the $300 but if you have friends going to camp together with you its better than sitting in school doing next to nothing. I hope this helps.
P.S. bring some sandals or thongs if you end up going because the bathroom floor is almost always covered in mud people shower after the mud course