George Orwell, from "Homage to Catalonia":

In practice the democratic 'revolutionary' type of discipline is more reliable than might be expected. In a workers' army discipline is theoretically voluntary. It is based on class-loyalty, whereas the discipline of a bourgeois conscript army is based ultimately on fear. (The Popular Army that replaced the militias was midway between the two types.) In the militias the bullying and abuse that go on in an ordinary army would never have been tolerated for a moment. The normal military punishments existed, but they were only invoked for very serious offences. When a man refused to obey an order you did not immediately get him punished; you first appealed to him in the name of comradeship. Cynical people with no experience of handling men will say instantly that this would never 'work', but as a matter of fact it does 'work' in the long run. The discipline of even the worst drafts of militia visibly improved as time went on.

I think this applies to teaching as well.