Do I always have to do two models? What if my objective is so easy I think the students can get it in one model?
Yes, always do two models. There are not many rules in this framework, but this is one of them. The reason for doing two models is the “whole-part-whole research.
We learn by making patterns. There must be at least two points of reference to make a pattern. It is similar to drawing a line. There must be at least two points to create a line. Two models allow us to begin to make a pattern.
Sometimes, with advanced students, we think we are holding them back by making them sit through two models before beginning guided practice. Even if that were true, the rest of the class needs another model. Two models will not hurt the students who understand a concept more quickly. But, it will hurt the students will need two models.