This paper describes findings from 41 studies illustrating why the concept of seasons is difficult to learn. The article is a nice supplement to CTS Sections II, III, and IV. IT also proposes a K-12 learning progression that can be used with CTS Section V that also shows the connections between global climate zones, behavior of light, and a model of Earth in space.
Sneider, C., Bar, V., and Kavanaugh, C. (2011). Learning about seasons: A guide for teachers and curriculum developers. Astronomy Education Review. Vol 10. Issue 1. http://aer.aas.org/resource/1/aerscz/v10/i1/p010103_s1