The Class Clown is...yes, Bobby?
"Please, Miss Friedland. Are they a really expensive circus performer?"
Yes, very funny Mr. Henley. Now, can anyone tell me why this trope is so popular? I presume you have something to add this time Bobby?
"Is it because it alliterates, miss?"
That's it, Robert Bernard Henley! See me after class!
This is about that one kid in the class who has to be the center of attention.
They're often a Keet or Genki Girl. Depending on how they're played they might be genuinely entertaining and popular, an Attention Whore or Bratty Half-Pint who everyone looks down upon or an annoying Jerk Jock. For added irony they might well become a teacher after a Time Skip. Sometimes you have pairs of class clowns who are Those Two Guys, school aged Fat and Skinny are most prone to this.
They're frequently The Nicknamer and Plucky Comic Relief, and may end up as a Non-Ironic Clown. In more serious works they're almost certainly a Sad Clown or Stepford Smiler, and may be the Teacher's Unfavorite Student. Sometimes some of them can be a little rough with their humour, skirting the line with The Bully at times.