How Do Things Change So Much?

My first day of school two years ago was my first day as a teacher. I was teaching fifth grade and my student teaching had been in Middle School, so it was my first time with the kids all day in one room. I had no idea how to make a day run smoothly with them all day. I had no idea how to plan enough stuff to last six hours. This year, I was writing plans for day one and I can't see how I can possibly fit everything I want to get done into one day. Sometimes I don't know how things can change so much in such a short time...