'Little Cloud Champions' mean ??

[choe]

I didn't grow up in the UK, so it's still difficult for me to understand all the messages I get from school ^^;;:

What does 'Little Cloud Champions' mean among Pupil Voice Groups?

It's nothing to do with not growing up in the UK; it's to do with your school making up a phrase. (See also "Pupil Voice Groups" which at least is reasonably self explanatory)
You'll have to ask someone at the school.