"Our heads hurt when we think"

Today two students came to me during independent work time and said together, "Our heads hurt when we think. We can't do the math." I laughed in their faces (tried not to, but failed) and they didn't laugh back....I think their heads really did hurt (for some reason half the class came back from music today with headaches--I think they may have been drumming). Nevertheless I explained that I was sorry that their heads hurt, but I couldn't excuse them from the lesson or from doing their work! ;)