Oh my gosh… maybe it’s been too long since I was at school, but I wouldn’t dream of replacing objects that were in perfectly good condition. Sorry, but I think replacing stuff for the sake of it is just ridiculous, and exactly what advertisers and marketers of these sorts of products want you to do.
I’m pretty sure no-one I went to school with replaced everything year on year just for the sake of it, and of course, if things got worn out (like bags), they were replaced, but this wasn’t necessary for everything. Maybe the schools we refer to are very different, or times have changed, but I really don’t remember anyone being teased about this at all.
In any case, I really wouldn’t feel right doing something wasteful on behalf of my child, just to avoid the bad opinion of someone stupid enough to tease another person because they didn’t re-purchase items unecessarily. I think it would send a really good message to your kids to replace what is worn out and keep what is perfectly fine, rather than sending the message that you will play into the hands of children who want to tease them by replacing all of their things. To me, that seems to avoid the issue rather than address it, and whilst I appreciate you don’t want your children to run the risk of being given a hard time, I think only replacing what needs to be replaced sends a far better message.
That’s just my view though, and it may not be appropriate for you or your children to do that, for whatever reason.