In secondary school, a few pupils had a "free period" during the day but they were very rare. For example, I started to study biology at the age of 14 but after one term (semester) I decided that I didn't want to continue and take the final exam. Instead of changing to a different subject, the two hours a week that I should have had biology lessons became "free periods" for me. During those two hours, I went to the school library to read (or to study) but there was never a teacher present in the room.
The only time that a group of pupils would be together with a teacher present (except for actual lessons) would have been "detention" - a 30-minute punishment period after the school day. If a pupil did something wrong during the day, the teacher could choose to give them "detention" - they had to stay behind for an extra half an hour, sometimes with other pupils who were being punished, but sometimes alone. There was always a teacher present at those. The punished pupils were normally given a very boring, pointless task to do for those 30 minutes.
Student or Learner