First I think you need to decide what you mean when you say preschool and programming. It can mean having everyone sit down in circle or at a table and go through a series of academic activities. It can also mean setting up the playroom so that there are centres or activities based on the academic skill available to the children. It means some one on one teaching which usually then leads into another child showing interest and joining the two of you. Taking advantage of these teachable moments can be more beneficial because they are built around when the children show their interest. It isn't always about what the children actually learn in terms of information they can give back but that they learn to love learning. The role as the teacher then is to find the resources to place in the room to accomplish the learning goals they have set. This could be things like setting out a cookie sheet and magntic alphabet letters, putting some dinosaur figures on the feltboard, putting a few books in a small bin but have several on the topic/theme you would like to introduce. One of the things I really don't like is when the "teacher" chooses a theme and then makes over the entire room to reflect the theme. What happens if the kids aren't as into the theme as the teacher and would rather do something else? It is also limiting in the sense that it only happens for a few days per year. Children in the 18 m to 3 y age range are changing way too fast. They need to experience the same "themes" over and over every few months as they have new skills to use in the learning. I think because we use some terms such as preschool and early childhood to mean different age ranges in different contexts it is hard to know what is developmentally acceptable for each age of child.