Hi,
There are many ways to get value out of an old light.
If you just want to get rid of them, put them on craigslist or free-cycle. You will have to do very little work to be rid of old parts.
There are metal guys in our area who will take anything from where they find it. In other words, you won't even have to move the stuff.
But, if you want to pull value out of old lights, read on...
To me an old light is...
a lamp - you may still be using those lamps somewhere, or put them in a box of 12 and eBay them.
a clamp - we still use the same clamp we used 30 years ago (with safety cables of course).
a plug - can be reused if it still fits your system. If it is a twist-lock, it may be the most valuable part.
a cable - usually recycled for copper or thrown away, old cables/wires are a bad risk.BTW, If the wires are covered with a white or grey fabric type coating (not black rubber), don't even touch the lights. Call your district or maintenance person and tell them you think you have asbestos. The offending lights will be gone very quickly.
The actual light which may have lenses and housing parts. Probably recyclable metal. The glass lens is desired by stained glass crafts people.
Unfortunately for me, I have trouble discarding any of these parts. But, luckily for you (maybe) is that almost all these parts have value on eBay. If the inter-district donation does not work for you, you may be able to recover some money that way.
I have sold old shop tools on craigslist and got some cash for the program at a time we really needed it.
John