Should be doing, Ought to be doing, Shouldn't be doing,
Oughtn't to be doing
Why is he sleeping now?
He should
be studying for his test.
Why are the children still awake at this late hour?
They should be sleeping.
Look! Those children are playing in the street, but it is dangerous.
They
shouldn't be
playing there.
They should be playing in the play ground. I'm watching TV with you now,
but in fact, I should be studying
in my room.