These covers from Miss C. H. Lippincott. I have to admit they are straying into "sweet" rather than "happy". On the other hand, I wouldn't mind seeing some of these kids at school!
My kids are sweet there, too, but in the last week of school they aren't as easy to deal with as these three images :-) (or as quiet).
This first one is a sweetie pie. Nice dolly face.
The eyes of these following children are weird!