It's hard to say. Why not approach them and start a conversation about something? Then it will be easier to tell.
Apart from that, you can return their peeks. Make funny faces when they look at you. Mime impersanate the teacher. Use your body language to make them laugh.
Don't cry, don't regret and don't blame
Weak find the whip, willing find freedom
Towards the sun, carry your name
In warm hands you are given
Ask the wind for the way
Uncertainty's gone, your path will unravel
Accept all as it is and do not blame
God or the Devil
~Born to Live - Mavrik~