Chaparones are ridiculous. Especially for teens. Believe me, I know.
I was the chaparone. I was the younger sibling and got put in the back seat and told, in no uncertain terms that if my older sister did *anything*, I was to report back to our Mother immediately.
My sister, older and meaner, told me in no uncertain terms that she would beat the s&it out of me if I told about anything that I witnessed. And, everytime we saw what she or her boyfriends thought was another car load of young people they would order me down.
"Head down, you fool!! They'll see you. They'll know you're with us you loser."
Making someone else go along was awful.
My sister recently brought it up, decades later. It still eats at her. She is still angry about it. She believes it was my fault our Mother forced me along on her JW dates. (When my sis dated worldly guys, my Mom let her go alone. No chaparone necessary. It was all a sham for the other JW families to feel better.)
So, teenagers will find a way. Don't kid yourselfs that having another person around is going to stop them from doing what nature is calling out. I was there. I saw a lot of it. It was ugly.