In reply to TonyB:
I teach in an international school that follows the UK curriculum and we teach those things in year 7. I have just been teaching about plant and animal cells and students have looked at onion cells vs their own cheek cells with microscopes. We take them on a trip to the local uni where they learn about sample prep and electron microscopy,so it sounds like that age group would fit in well with what you are doing. What you're looking to do sounds great. I wish there was more of that sort of thing...the kids at that age are really keen and have natural curiosity...so they'll love it. If you fancy doing it abroad drop me an email!