I think the word you’re looking for could be dadais.

Then, the bad-mannered part is optional, and should not be seen as Tom Sawyers’ bad manners, just that as a matter of fact that young man has bad manners from his clumsiness most probably. This makes a fundamental difference with the words already mentioned in the comments, which all really match some kind of bad intentions from the kid. (say, as much as a kid could have bad intentions)

“grand dadais” was usual, but didn’t mean bad manners, only silliness and clumsiness.

Typically a teenager whose body grew faster than sagacity. That is the reason why it is rarely used without “grand”.