You will notice that when the teacher is speaking to the whole class there is an -ibh at the end of verbs.
They say:
Thig a-steach! to one person but Thigibh a-steach! when he asks the whole class to come in.
Bi modhail! to one person but Bithibh modhail! when the whole class is misbehaving!
Mas e do thoil e is how you say please to someone you know well.
Mas e ur toil e is how you would say it to more than one person or to someone when being polite.
