I purchased a small Chain Reaction Kit from Lakeshore Learning with money from PTO. The kids loved it so much I purchased two additional larger kits. These are great for teaching cause and effect. They are great for a 3rd grade forces and motion unit. I also like how they encourage perseverance and following directions. I put out the "easy" level cards first and then have students progress to the "medium" challenge cards. The "advanced" cards are really tough!
It is funny because the kit says for in grades PreK-2nd but these kits challenge my 7th graders too!
I love kits that work for a variety of ages and challenge students again and again. These kits are a favorite and I was able to get them with a buy one get one 50% off coupon. They are expensive kits so the discount was a big help.