Back in the early 80s when I was in grade school, I remember using a resource I believe we referred to as 'Challenge Cards.' The cards were contained in two or three boxes, each box with two or three columns of cards. Each card contained a different puzzle or riddle designed to make you think. The cards were categorized by difficulty and had a stripe of color running across the top. Light blue cards were easy, deep purple cards were hard, and there were red, green, and other colors along the way.
Now I'm teaching my own child, and I'd love to locate this resource. I've been trying to find these things for years with no luck. Does anyone know what these are called and where I can find them?
Thanks.
