"Rebelión en las Aulas": Where's the Key?

Last week, when I was about to go to 2nd of Batxillerat class, I can see how the corridors are crowded with students and teachers. I thought, as you might all think, that nothing special was happening. But for my surprise, the students of 4th of ESO were locked in their classroom. Just to let you know, this class is the one I'm following.

Do you want to know what happened? I was just about to tell you, because it's been an experience for me!

During the English class in the morning, from 10 to 11, they had an exam. Apparently, my tutor had to leave the class for a few minutes and when she got back the classroom was locked. The only possible explanation was: They have a key.

And I stop here to tell you that all the classes need a key to be opened/closed. So, the students of 4th of ESO have a key! Where did they get it from? Nobody knows... But the point is that at the end of the morning classes at 13:30, the head of studies orders one of the teachers to lock them up. Obviously, once they see the door is closed they start to knock heavily at the door, shout...some of them behave like savages!!
One of the teachers who is standing outside the classroom decides that it's not legal to keep them locked so she (and a few more teachers) get in the classroom so they can talk and find a solution. Some other teachers think that if the students have the key they should use it to open the classroom.
Well, at the end, the person who had the key didn't show up (as all of you can imagine), but the day after the key was found in reception.
I know that a lot of students were angry at the person who took the key. They say that he was a coward not telling the truth when he had to.
So, what you think?