Hello CeaselessMedik,
When I was in High School, I used to be part of the Diocesan Youth Evangelization Team which ran the Diocesan retreats and rallies for Middle School and High School. Really, there are three different types of retreats that are offered for later teens.
The first is somewhat of a rally retreat. These usually are for large groups of teens. The smallest one of these I helped put on was for about four hundred High School youth group members and the largest was 650+ students with about 100 chaperones and staff. These are centered around primary keynote speakers and have large scale meetings, but also break off into smaller sessions on various topics the teens can choose from. It was usually a very up-beat atmosphere and had a christian rock band and games filling the time between the sessions so that the participants wouldn’t get restless. There was, however usually a designated time for solemnity. Ours usually were the large group adoration (in addition to a smaller adoration chapel which was open 24/7), a specific time for Confession availability, and a group mass (usually with the Bishop).
The next type of retreat was focused upon discussion. This was generally smaller, usually being no more than 100 participants. We would have large group sessions on specific topics that teens encounter in their daily lives and then break up into small groups to discuss these issues and address any problems or questions the participants have. The retreats were centered around these small groups and they became your family for the duration of the retreat. There can also be very upbeat, but the focus is upon the social aspect of our Faith and putting it into practice. Again, there were times set aside for adoration, confession and mass.
The final type is a silent retreat. I personally did not help lead these retreats when I was on the Evangelization Team, as they are centered upon building up your own spirituality and knowledge of self. They are usually conducted by those who have a lot more experience in the spiritual realm than High Schoolers. I have, however been on silent retreats. Usually, you will come together for talks with the other participants. Sometimes you will discuss your meditations with the other participants, but sometimes it is strictly personal. You are usually given a large amount of free time to meditate upon your talks and use as an opportunity to deepen your own spirituality away from the world. Again, no retreat would be complete without mass and usually there is at least one time when a priest would be available for confession.
Hope this helps!
God Bless,
Br. Ben