I'm also a teacher and I've tought about having a summer job. I haven't been able to find one but I wasn't very persistent, too. But when I definitely wanted it to be something without responsibility, something for fun. You just need a break. I wanted to distribute flyers or promote something in stores: just stand and smile and offer people to try a new brand of something. Also I wouln't mind doing something manual or in agriculture: picking fruit or vegetables. I've done this and the feeling when you are tired is so different from the tired from teaching or doing something mind obssessing. When I used to work manual labour, I went home tired, took a shower and then became brand new and relaxed. I went out to pubs and enjoyed. Well, I was younger then, maybe that is also a factor.
Good luck and keep trying. Have something for fun, don't look for big jobs, big money or big responsibilities.