Agree about schools being more demanding other tban extrovert kids. When i was at school group work or helping was called cheating. Now i have seen group work where one person did the lion's share of the work but everyone was assassed together. Writing that used to be between you and tbe teacher is now peer edited etc - I didn't want to share anything personal with bullies and i imagine it makes many kids more cautious. Classrooms were for the most part quiet and orderly.