Australia

Teachers are limited in what they can do. They aren't magic - they can't just snap their fingers and create different beliefs and good behavior. They can't spend their whole workday trying to un-brainwash a single student. And even if they did, they can't follow that student home to continue this work. With limited options to actually change a student's point of view, they are left with options to simply curb the behavior so they can get on with teaching.

However, these options are also limited. They can enact small punishments in the classroom like taking away certain privileges. Or they can send the student to the administration for some kind of punishment like detention. These punishments typically don't result in significant behavior change. Schools have the option of expelling students, but this is heavily frowned upon by higher-ups, as it puts more strain on overtaxed "second chance" schools, and often brings the ire of parents.

So the teacher ends up stuck with a misbehaving student without the time or resources to effectively change their mind or their behavior. Blaming individual teachers is... dumb. It's really dumb. Teachers are there to teach, and to handle minor disciplinary issues. They need more resources to handle bigger issues like this.