I haven't read all the posts here, so forgive me if I am repeating what someone has said...
There ARE ways you can get permission to take your herps to a school within the limits of the law. I'm a teacher and have looked into the demonstrator licenses, but decided it was not for someone who just occasionally presented about snakes. Folks who have obtained that license have taken a lot of trouble and expense to get it!
If I want to take some animals to a school or other public place (the local Probus club invited me last year), I write to the licensing authority and explain what I want to do and what animals are involved. They give me permission for that particular event and we are all legal and happy. If you plan ahead, it's no big deal. You do, however, have to think things through ahead of time. The Animals in Schools regulations in NSW (can't speak for other states, as I haven't read them) allow you to bring in reptiles and show them, but you still need permission from DECC.
If you want to keep a reptile in the classroom, you have to jump through a different set of hoops, but it can be done, too. As snakehandler says, read your license conditions. Learn the laws and regulations, which may come from multiple sides (DECC, Depatment of Education and Department of Agriculture in NSW). I've just prepared the renewal for our school's scientific license which allows us to keep reptiles. It is a hassle, but definitely worth it. The students learn a lot just by having the reptiles around. It counteracts common prejudices and ignorant assumptions. It also serves as a great way to expand our hobby to the next generation of keepers. I love having a MD in my classroom and use him in class whenever possible!
