We learned how levers and pulleys allow you to lift objects more easily before making our own simple and compound pulley systems. By using cereal boxes, pencils, string and paper clips, we discovered that adding more wheels  to our pulley system reduced the effort to lift a weight. The children then extrapolated this information to other pulley systems with more wheels. 
 

I owe thanks to all the children who brought in cereal boxes and to Mr Fairbanks who allowed us to use his washers.