This is the first year we have a group of third grade teachers using Investigations. They are using the books in order listed on the back. I am a math intervention teacher and this order doesn't seem right to me. We completed Things that come in Groups and Flips,Turns and Area. Now we are going to do Landmarks in the Hundreds which seems to have better preceded Things that come in Groups. I really feel there should be some sequential order to the books taught in each grade. What do you suggest?