Waddlers

So paired with my new job title is a new classroom. I am now "teaching" a classroom of 12-18 month old. I use the word teach loosely.  They are beyond cute.  I adore each and every one of them. However, I do have to change diapers now. At first it wasn't a big deal, but it really starts to wear on you. The other issues I am facing is how to discipline someone so young. I can't count the number of times a day I say "Ouch! That hurts my friends. Show me gentle" or "Biting hurts!!"  I am really unsure of what else to do. So please pray for me as I enter these uncharted waters of babysitting both children and adults.