Girl, please help me, is it appropriate to send this text message?

Inappropriate...

Maybe you can consider sending it like this:

I just want to be good to you, and I don’t expect anything in return from you, let alone I hope to be your boyfriend. I just want to watch you from a distance and guard you. When I leave this school next year, maybe I will go quietly, but I will still be guarding you somewhere in the future.