Teachers in our school, and many others, work hard. Real hard! There just isn't enough left in the tank at the end of the day, or during an after school meeting, for them to focus the amount of energy to do all the planning and revising necessary to make significant improvements to their instruction. The professional learning days embedded during the school year are often jam packed with even more new things for them to learn and do. Not allowing them the time to work that they so desire.
Many of my teachers took advantage of the summer break to do some intense work for the last two weeks. Kids were done, and some teachers were done, but a few dedicated teachers stuck around and got some planning for next year done. Very inspiring to see what they've accomplished.