Public speaking is the most common fear of young language learners. - quote from myself
If you do not believe this, I challenge you to teach foreign languages in a secondary school. Even having a presentation or a speech in the native language tends to be a hard job to complete. I do not mean the gibberish chatting, but the stress in class when a pupil wants to speak in public. Therefore I advise parents, other teachers or educators to let their children or pupils speek freely. Correct when it comes to swearing, but do not ban them from speaking in general. This could lead to faltering or a total mind-stop, when pupils have to answer questions. Another is of course a lack of courage. Pupils must learn they mean something, they are important. So an additional good idea would be creating a class identity and atmosphere in which individual pupils make the difference.
For teachers, they have to pay attention to not use too much academic language. You do not have to ban it, but you can try to rephrase yourself when it occurs to you.
A good film about a class identity, but rather one about how-it-is-not-done, is Die Welle ( The Wave). It is a German production about a teacher who wants to prove if nazi-Germany can be re-constructed in his class, based on true stories.