Should slang be banned in schools??

Writing my opinion to the following artical -
https://www.theguardian.com/commentisfree/2016/may/03/dialiects-slang-children-language-english

One argument in this article is saying that slang words should be banned in school and that parents and older people need to teach their children to stop saying words that aren't 'proper English'. 

Whereas the other side of the argument is trying to say that schools have been trying to do this for "more than 100 years to no avail" and that children should be allowed to use slag words in social settings and that they are mature enough to not use them in a context that would have an impact on their future life for example a job interview. 

The first argument has many different facts and opinions to put forward which would help them fight their own corner. As an example of this Ongar Academy have said that 'they are not banning words but "evolving" their pupils speech' David Grant the head teacher has said that students' dialect "may not favorably reflect on them when they attend college and job interviews. 

As a counter argument they have come back with many ways to contradict their points. For example they have said it would be hard to show children what they shouldn't be saying whilst at the same time trying to teach the children that there is nothing wrong with their natural expressions and dialects. They have also said that assuming students who use slang (most of them) would use the same slang words in a formal situation is a disservice. They carry this on by using different examples such as "we may wear a t shirt at home but a suit and tie at work" they use this example to suggest that the words you use with friends whilst you are out is different to words you would use in your workplace talking to your bosses. 

In my opinion I strongly agree with the counter argument because now a days children and students are so sensitive to how they are perceived from a peer or an older figure that punishing them for using their every day speech can be extremely harmful, and it could possibly do more harm than good. I do agree with the first aggument slightly but instead of banning students from using their everyday language that they teach them the correct context that they should be used in.