My daughter's project in maybe 6th grade or so was a wind tunnel we built out of an old furnace fan and some plywood necked down to 6" x 6" in which we rigged up a reaction arm leveraged to depress a postal scale. We had three easy to attach 1" thick profiles (round, square and streamlined) and I rigged an old airplane airspeed indicator up to fancy it up a bit (it was a big fan and would produce 60mph). We got very nice numbers from it that easily showed the huge difference between the different shapes. She wrote up some stuff about how important aerodynamics is when designing efficient vehicles.
She advanced to the next level with it.
One could probably do this using something simpler like a leaf blower..... Just be sure that it is set up in a direction that it will not knock over everyone elses projects.
