Depends on the kids, the chaperones, and the length of the trip and what the schedule looks like.
I went on an overnight field trip with my daughter last year, for the very reason you are concerned about. There would be girls in a room with no chaperone. Turns out, they would have been fine, but I didn't know that beforehand. It was a very small group, 2 boys, 2 girls, and the adult teacher/chaperone. The boys had a room across the hall from the teacher (who had his own room), the girls were the room 2 down from the teacher (so no adjoining wall). The teacher put an indicator outside the boys' room so he would know if they exited their room after hours. They were out late (it was a band trip and they had 8 hours or practice time on day 1, split into 3 time periods, 2 early, one late one after dinner). When we returned to the hotel, everyone was tired, and was expected up and ready to go early in the morning for the early morning rehearsals. My daughter's roomate was a very mature and responsible young lady. One of the kids that you see leading everything.. President of Jr. Beta, this club, that club, fall sport, winter sport, spring sport, top scores on tests, most volunteer hours, etc.
Daughter is very much like this other young lady. They would have been just fine.
But, it was a very small group. A large group would make things more complicated. 4 kids to a room could be fine... if the kids are responsible kids. No one ever has to go anywhere alone, and no one would be able to do anything that someone else didn't know about. But, if they were all "in on it"...