Teaching is hard. Can I just say that for a second? Teaching is incredibly difficult. It's not any one thing that I can point to that makes it hard; there are a ton of little (and big) things that make it challenging, and the fact that teachers have to overcome the same challenges for 180(ish) days per year makes it exponentially harder.
One of the problems teachers have is a general lack of focus. Imagine it. You're looking out at roughly 30 young people. At any given moment, maybe 2 have their heads down. About 5 or 6 are doodling. Eight kids are looking right at you, but 3 of them seem to be staring past your head. One has his hand up, probably wanting to go to the bathroom. Several of the girls are glancing at each other out of the corner of their eyes and giggling or fighting smiles, assuming I don't see them. Two of my boys are trying to get comfortable in their seats, squirming or leaning their chairs back on two legs, despite my daily telling them to stop. One is sharpening a pencil, while one returns from having gotten a drink of water. The rest all go back and forth between looking at me, looking around, scribbling on their papers (is that math homework I see?) and whispering to a friend. How many of these kids are being quiet? Most of them. How many are looking at me? More important, how many are really hearing me?
The thing is, focus isn't something you see as much as something you feel. With my kids, I know that the doodler in the corner might be listening, while the one looking right at me is actually focused with every ounce of her being on the cute boy right behind her. I'm not nearly as concerned with what the child is doing as with what he/she is focusing on. I really believe that God is the same way. I don't think he needs us to pray 24/7 or worship 10 hours a day or read a book of the Bible each evening. I think that God just wants our focus no matter what we're doing.