This unit is a big one! The TEK is: classify and sort two- and three-dimensional figures, including cones, cylinders, spheres, triangular and rectangular prisms, and cubes, based on attributes using formal geometric language.
The 3D is not too bad, but understanding the 2D is kinda crazy! In second grade they classified based on number of sides. They learned to count the sides and name the figure. This year, they will be looking at new attributes- the side length, sides that are equal distance apart opposite angles that are congruent and square corners. This is the year students learn about equilateral, isosceles and scalene triangles. They learn about the attributes of quadrilaterals- parallelograms, rhombuses, trapezoids, rectangles and squares. They learn about the attributes that help classify these shapes. It is important to teach students to identify shapes by their attributes and not just by recognizing the shape.