When I was in school, almost no one actually said the pledge. By the time I was in high school almost every just sat and continued doing what they were doing. This was in a conservative suburban school in the south.

It's not surprising to me that it's variable. The school administration, culture, and individual teachers matter a lot.

For example, a Colorado teacher physically assaulted a student for not saying it: https://kdvr.com/2018/08/31/teacher-accused-of-assaulting-st...

Another teacher just tried the guilt trip approach: https://fox2now.com/2018/11/16/teacher-banned-after-students...