For streamer choice I would probably go w/ something like the Blacknosed Dace. One or two deer tails, a little tinsel and you have all the materials for a whole fistfull of tying without much materials cost. A good fishing pattern too. If you have a red squirl tail or two, you might consider the Shushan Postmaster ( by Lew Oatman). just as simple to tie, something the students would not be likely to get "store bought" and an excellent fishing fly which seems to have been forgotten except for a few cranks like me.
One thing you might encourage is the use of materials your students might be able to get from hunting or from folks they know who hunt. Lots of grouse hunters don't fish or tie and would be happy to part w/ the makings of the classic Partridge wet flies, Partridge and peacock, Partridge and Orange, etc.
Turkey hunters, squirl hunters, deer hunters are all possible sources of excellent materials. Also check out the thread on cat hair. Any knitters in the family? A few feet of angora yarn, white wool ( Edison tiger body) etc. can usually be found in grandma's knitting basket.
AgMD