Mamasource from Mamapedia is offering a 50% off deal on the monthly science kits from The Magic School Bus: you can get one year (12 month) of science kits for $120 (an average of $10/kit).
The kits are mailed to you monthly and each month’s kit has a different topic. The kits contain most of the supplies that you’ll need to conduct the experiments, with the exception of some things like vinegar or sugar. (Anything that most people wouldn’t keep in their kitchen is usually included in the kit.)
I ordered this kit last year and we really liked it. My kids love doing the experiments, and it’s definitely enabled me to do way more experiments than I would have had the time or energy to do on my own. Call me lazy, but it’s nice to not have to buy random things like iron filings or foam balls to do a science experiment!
I’m sure you could buy the supplies cheaper elsewhere, as long as you can find a source and would be able to find a use for the leftover items (since many experiments use only a tiny bit). I used Groupon referral credits to purchase mine when a similar deal was available through Groupon so I’m not sure if I would pay cash for it because it’s so much at once. But, it’s probably still a lot cheaper than buying all the items on their own, and it was a good motivation to me to actually do some experiments.
Each kit contains a booklet with a brief overview of each topic and a place to journal your observations about the experiments. Though it’s nowhere near in-depth, I did appreciate that the booklets contained a pretty good scientific explanation of what you were doing in each experiment. (The books of science experiments that are fun, but don’t give you any sort of explanation as to what is happening kind of drive me nuts!)
We got behind on doing our experiments, so I just stopped in April and saved the kits we received to use once we start school again this fall.