Watch the shirt rack that Zora "disappears" behind. You can see her walking behind the rack.
Notice when Zora draws the circle, if you can see it, she clearly draws it on the bottom right, but when Sonny stops daydreaming, you can see it's in the middle.
At one point, Ms. Bitterman tells her class to think of a trapezoid as six triangles. However, a trapezoid is the same as three triangles, not six.