My school had compulsory Confession once a month (compulsory confession - a contradiction in terms). Some kids just started making up sins to tell. Others assumed that as they were required to go to confession monthly, then they must be doing bad things monthly somehow. What those bad things might have been they weren't really sure, but remember that there were (and still are) 2624 "sins" against the "Six Commandments of the Church" ("bishop's sins"), and then the telephone book-sized list of sins against the 10 Commandments.
Curiously, although diocesan priests were very busy with a heavy workload, the school didn't seem to have any problems getting priests to come in from outside the parish to hear the confessions of adolescents and pre-adolescents. Now, I wonder why that was!