1. Geometry Progressions
Irene, Vince, Renée

3. Shifts in approaches to content
3D visualization (7th grade plane sections) as a way of understanding volume
Big ideas are developed in terms of transformations (instead of congruence)

4. Differences from current practice
congruence described in terms of rigid motions
similarity described in terms of transformations
similarity, congruence moved to grade 8 (with conceptual introduction in grade 7)
plane sections of solids moved to grade 7
students in grade 8 explain proofs of PT & PT converse
students in grade 8 explain proof of Triangle Angle Sum Theorem

5. Surprises!
Formulas for volume are given and used in 8th, but the explanation for why they work is a high school topic

6. Implications for Teaching
Using manipulatives and technology will help students understand/visualize similarity, transformations, and congruence
Teachers should establish connections to other domains like ratio and proportion, expressions and equations, number system, functions, and statistics and probability
High school teachers should plan for some students to have more rigorous experience with big geometry ideas than in the past