External Monitor changing resolutions on Macbook

I have seen several people ask this question, but I haven't found a suitable answer. I have a MacBook running 10.6.8 at school. I teach and move from room to room hooking up to different projectors and monitors. The set up is just very unstable. Despite its supposed ability to remember settings, it rarely does and the resolutions are messed up as well as the display callibrations. I have an external monitor on my desk. Yesterday, I set the resolution to the native 1280x1024, when I plugged back in, it was back to 1024x768. For some reason, the higher resolution wasn't even appearing on the list until I fiddled with it.

Why is this so buggy on this MacBook running this OS? Is there a way to force it to remember display settings better? Any tips?

I know that other teachers have more problems than I do because they don't even know how to change resolutions or anything like that.

Thanks for any tips, tricks or helpful comments.