These are the three types of hooks I've tried. Do-it-yourself good old paper clips bent every which way, purchasing the clips that slide into the ceiling (Too expensive! But, I will continue to keep a few around for the heavy solar system pieces), and my little magnetic paper clip.
Supplies you need: magnets, hot glue, and paper clips.
Simply hot glue the paper clips to the magnets, let them dry, and hang them from the ceiling. When hot gluing, I took my time and supported each paper clip until the glue hardened enough to let it stand alone. I was able to make about 50 of them in an hour.
These easily hung a food chain craftivity. Granted, they won't hang heavy things - like an inflatable sun or most of the planets. But, they're good when you have 50 student projects to hang from the ceiling.
Oh, and to get them up there without using chairs - run over to Dollar Tree and pick up one of those long-handled tools with a claw on the end to pick things up.