Ten, nine, eight . . . three, two, one . . . blast off! Few things are better than launching rockets to get a kid a child to want to play outside, engineer, and then run around. The thrill of the countdown, the endless customization of building the rocket (3 fins, 4 fins, maybe even 5!), the chance that it could land on the roof, are just a few of the joys of building and launching paper rockets. Build the rocket launcher, or two, grab a bicycle pump, and turn some junk mail into paper rockets. 
Build a Paper Rocket Launcher
Use the directions in this pdf to build the launcher. I’ll make the directions or a video on this website sometime soon (4/14/18).
To obtain the bicycle tire stem, swing by a local bike shop. Ask them if they have any trashed tire tubes. I walked in to my local bike shop, Treads!, and went straight to the shop to ask, “I was hoping to get a few Schrader stems for a PVC project I’m working on, do you happen to have any trashed bicycle tire tubes that I could have?” The guy handed me three tire tubes, and let me use his scissors to cut the tube on either side of the valve stem.
Cut a few lengths of your leftover 1/2” PVC at about 12 inches to use as rocket molds. If you are a teacher, probably cut more to use with your class.
Launch some Paper Rockets
If you have some 1/2” PVC forms (the same size as the actual launch tube) tightly wrap your paper around that and tape it on the top and bottom to get your rocket body correctly sized. Once that body is formed so it fits on the launchpad, everything else is up to you.