If you focus on teaching, you might think different method and practice to teach students. In addition, you might work on different ideas while facing different environment that have limited resources. 

Some people in the city might say that using chalk is might be harm for health but it is too useful in the village. I realize that coal is work to write by using with thin wood board while you are out of school supplies. 

Especially, I notice that I use the rock with some rock color for writing while we stay in the forest as there is nothing to use for study. At least, it works to study compare to you have nothing.