This last batch of chicks I hatched out over the winter used to huddle up along the outside of the coop at night, even after I had them locked up in the coop for a week (and even having the 5 adults showing them when to go inside). I started feeding them in the evening, as it was getting dark, and they figured out they should go inside at night, since by the time they ate enough to satisfy themselves, it was already too dark for them to want to go back outside.
I still feed them in the evening, but at least a couple hours before it gets dark and they still remember to go in before dark. They're even learning to get up in the rafters before it gets too dark for them to be able to see to get up there (I don't have any windows in the coop, since it's a converted shed).