In seventh grade I created a Science Fair project that wasn't very original, but it did get a lot of laughs. I came close to getting in trouble but I played ignorant.
Did you know that the fizz created by a Menthos candy pebble, when placed inside a 2 liter soda bottle, actually causes some kind of chemical reaction? Well, it does!
I got together with two of my girlfriends and decided to do a very detailed experiment. The quality of of our graphs and research is what saved us from failing. The actual experiment conducted on school property was frowned upon.
If I had it to do over, I would have video-taped the various experiments and played them on a portable DVD player rather than let the explosion happen in the cafeteria. There wasn't an actual explosion, but a mess was made, nevertheless. The fact that putting the candy in the bottle caused a reaction and caused the fizz to burst through the top was very interesting to all the other kids in the class.
The science behind it impressed the teachers. What we did was got several types of soda and several types of candy. We monitored the insertion, the quantity of fizz that was created and the reaction if any.