I don't think ages have been announced, but I'm assuming High school age based on the interactions:
Magical girl high/middle school (I'm not super far into it, but it's been good so far)
If I recall the characters are in high school
Characters are 13
Currently on a hiatus of some sort, but still worth the read
Super hero summer camp:
I don't know if it's going for any action/adventure, but still worth the look
And I'll post mine as my main protagonist is 16
Hopefully at least one of these are of interest. I personally like all of them.