One of the largely unacknowledged issues around the rise of poor behaviour in secondary schools is the lack of teachers. Lots of discussion of the lack of TAs, or pastoral staff, or mental health support, but not much about the day-to-day experience of kids who are being taught, for not an insignificant amount of time, by cover teachers. Teachers who don't know the subject and are just babysitting the class, or teachers who don't know the subject and regardless are expected to attempt to teach it. Teachers who don't know the kids and who change on a daily or weekly basis.
People who want to get rid of isolations or whatever always focus on building relationships with the kids. Supply teachers don't even know their names.
Behaviour in my school is noticeably affected by kids having cover lessons. Kids come to my class saying 'you can't expect me to behave, I've just had a morning of cover'. Kids generally like, and respond well to order and routine, but order and routines take time to establish, and are more difficult to establish if kids bounce into your lesson high as kites because they've been pissing around for the last hour.
Bennett is one of the behaviour experts who recognises that while good relationships with the kids are something that teachers should be aiming for, behaviour management systems should be usable by a supply teacher meeting the class for the first and only time. And that is increasingly important.
If you want to improve behaviour in schools, massive investment in a stable teaching workforce should be as much of a priority as improving SEN and mental health provision.