It's better not to teach something at all than to teach it badly.
Nothing lasts forever.
Even the poorest and most defenceless will tolerate only a certain amount of abuse or contempt.
It takes only a small, last thing to break the endurance of someone who has suffered much for a long time.
The world needs workers. Not everyone can be upper-class, rich or idle.
Everyone is born equal and has equal rights.
You should do as you say. (Do not tell others how to behave but ignore the advice for yourself.)
All people are equal.
Treat others as you hope they will treat you.
If you want to do something very well, then you will need to practise and practise.