Immature edits by immature people 

Your proposed "cheerleader editnotice" is a strong, not-very-friendly solution to a problem that historically has been solved with honey.  The historical way of dealing with editors who are immature is to watchlist articles likely to attract them, revert them, kindly explain why they were reverted using a welcome template or an individualized note, and point them to the right way of doing this.

Wikipedia is largely edited by adults, for adults, using social constructs familiar to adults.  It's not MySpace or cartoon-pedia, or AllThingsDisneyWiki.com, and it's not a teen hang-out or kid's playground.  The social rules that junior high and elementary school students use day-in-day-out are quite different from those of Wikipedia, and WP:BITE says we have to be understanding of this and use a velvet glove approach.

I don't run across very many editors who "seem" young by their edits, but most of those I do don't last long.  I can understand why - socially, it's just not a good fit.  A my-school-pedia about their school and town, edited by them for them, would be a much better fit and much more enjoyable for them.  /(talk)/(contribs)/(e-mail)