I don't really understand how people think they are for "little kids" because they are actually kind of difficult to take care of!
I bought one for my 4 year old sister at Christmas, (it was a v4.5) and she loved it to bits, and kept it alive for a few generations, but it was difficult for her to use (especially because she cant read) and it eventually died.
So, tamagotchis aren't really a childish toy.
And I've taken mine to school before (of course I hid it in my purse).
At my middle school, loads of girls in my class had a tamagotchi (this was when the v2 came out. I was 11 or twelve). But they didn't like them as much as me and my friends did. Eventually my friends stopped using theirs, too.
I like to take mine out in public now, just not to school. Sometimes when we go out to eat I'll set my tama on the table or I will play around with it while we are waiting for our food.
I still use my tamagotchis around my friends. They dont really care. One of my friends actually bought me my first Music Star for Christmas!
I guess it doesnt matter if you play with tamagotchis as long as you have good friends and hide them if you use them @ school