For Halloween: Casting with packing tape. First layer sticky side UP, then Using just the legs for halloween would be fun. layers sticky side DOWN. Round tip scissors to remove, then tape back together.
Kids dressed as SHADOWS for Halloween - their mother bought black morph suits for them then layered black clothes over those. She says, This might be the easiest costume on earth. I love this idea for halloween next year
How to make your own air dried porcelain with common household ingredients 3 cups of white glue (PVA) 3 cups of cornstarch (Corn flour) one tablespoon of white vinegar one tablespoon of glycerin (health food or hobby shop), and 2 tablespoons of canola oil
Make your own tinfoil portraits/sculptures. You could buy face masks and give students tinfoil. I think this would work. Would probably look even better on a black canvas or cheaper option, black card.
Vaseline and caulk to make small molds. For reproducing small details, coat the original with Vaseline, then cover it with a thick layer of 100 percent silicone sealant. Let it cure, remove the mold, and fill with plaster of paris.
Spray cheap halloween masks with glow in the dark spray and watch your haunted house light up where ever you put them. Leave them in large groups or use only one or two. Either way it's cheap and CREEEEEEPY
3 Super Easy and Innovative Plaster of Paris Recipes