Dipping ordinary paper snowflakes in wax will not only give them a subtle sheen, but will also make them durable enough to be used year after year. In addition, it makes them somewhat waterproof so that they will not be ruined by condensation if you put them on a window.
After you have cut your snowflakes (here are some excellent directions on how to make the really cool 6-sided ones), slowly heat household wax in a frying pan or a plug-in warming tray over low heat. Use an old pan that you can dedicate to melting wax, because after this, that is about all it will be good for. Once the wax has melted, lay the snowflake in the wax.
As soon as it is covered, use a tweezers or metal tongs to lift the snowflake out of the wax. Hold it over the pan and shake it gently for a few seconds until the wax stops dripping and is mostly dry. After about 15 seconds, you should be able to put it onto a plate and it can be handled within a minute.
That's it! Of course if you are working with children in a classroom setting you will need to be extra careful, but I first learned how to do this in a kindergarten classroom. The teacher used a warming tray and the children knew they had to stay away. You can do dozens of snowflakes with a single block of wax.