Is there a place for sheng in schools?

Many years ago, when I was in primary school, there was something called a disc. A disc was basically a dirty smell bone that was used symbolically. Anybody who spoke Kiswahili or their mother tongue, had to endure the embarrassment of carrying the smelling bone for the better part of the class day.

Everybody hated being subjected to such humiliation and so we all did our best to speak English broken as it was. Kiswahili is the national language and so in retrospect I wonder why they used to discourage us from communicating in this language. Anyway I digress.