Classroom management is a massive subject, endlessly written about, but the teachers with the most effective classroom management have generally trained their classes in what is expected of them. The children are fully aware of how they are expected to behave and the consequences for not fulfilling those expectations and race/class doesn’t come into it.

There are behavioural issues that need specialist treatment, but most children don’t have those issues.

It helps if the school management has bought into the idea of a school-wide behaviour policy with a progressive ladder of sanctions up to and including exclusion/expulsion.

It also helps if the staff at large, from teachers to custodial staff, buy into and apply the behaviour policy too.

Things that undermine school wide behaviour: Teachers applying their own behaviour policies (including having their own rules).
Teachers who want to be friends with the students.
Teachers who think black/working class/french students are incapable of behaving the same way that white/middle class/English students behave.
Teachers who are not supported by management, management should write, implement and enforce a school-wide behaviour policy and then empower the staff to follow it.
Teachers with poor classroom management skills, I’ve watched countless clips of incidents in US classrooms and the common factor in all of them is terrible classroom management. I saw a clip recently where a teacher got struck by a flying chair and was knocked out and hospitalised. The teacher had ample opportunity to stop that, the girl who threw the chair was clearly in the midst of a tantrum, but instead of addressing that issue before it escalated, the teacher ignored it and actually turned her back on the girl. The teacher showed that she either had no idea of what was going on in her classroom or she had a serious lapse, but either way she put herself and her pupils, including the chair-throwing girl, at risk of injury.

Classroom management is so ridiculously important, fail at that and it doesn’t matter how good your planned lessons are, you’ll never teach a damn thing.