From what I understand, schools that want summer camps may still asked their NEST teachers do to them, but recently camp position have also been filled by recruiting companies who bring foreigners over for one or two weeks as "volunteers". The foreigners aren't paid, but their flight is free, so I'm not really sure if anybody saves money this way. I don't know if that is what is happening with everyone, I just heard about it happening last year. My school doesn't do summer camps, never has, but I work at a high school.