So пара means a pair of classes going in sequence at the university/college. That's academic slang and both students and professors say that.

Assuming, втыкать means when your thoughts are being somewhere else, so that you no longer pay attention to what's going on around you... - which is teenager/student slang (presumably, not the best students)

one can translate it as 'Being somewhere else (inattentive) during classes'

Frankly, Valda, i wouldn't understand what this means if iCake hadn't shed some light here...
So personally, i would refrain from using it))) Well, maybe for fun.. just to sound like a teenager.... Valda מילה זו היא מאוד טפשה! ממש טיפש!

But the word ПАРА is OK...