Did the notion of "Youth Group" exist in the early church? Some modern churches have the notion of a "Youth Group", it is characterized as the following:


a dedicated "Youth Pastor"
consists mostly of younger (middle school + high school + college students)
a bit more modern in worship (drums + guitars)
some belief that adults / youth should receive different messages


I am not aware of any such distinction mentioned in the new testament.

Is there any historical evidence that "Youth Groups" existed in early church history?
In Catholicism "youth ministry" is so recent that it was not available when I was growing up. We had CCD, which Protestants call Sunday School, but we were still expected to attend Mass with the adults. CCD was scheduled at a different time, and not always on Sundays. Students who attended Catholic schools did not have to go to CCD because they received religious instruction in school. These days many parishes (including my own) treat children like catechumens in the ancient church. That is, they attend the first part of the Mass (the liturgy of the word) with the adults, then they go off with their instructor to a classroom for a youth ministry of some kind while the adults have the liturgy of the eucharist. This never happened before Vatican II reformed the liturgy. The ancient church had no idea of a youth minister. Usually a parish only had one priest, so the catechumens would have been taught by a deacon. But the catechumens were usually adult converts. Children were baptized as infants, were taught the faith in the home, and attended the Mass with their parents even as infants.