I've found that it makes no difference whether you confine chicks to the coop or not in order to teach them to go in when night comes. This may work splendidly to teach grown chickens to imprint on their new coop, but chicks are different in that they are small and inexperienced with the world, and they have a natural tendency to resist going anywhere that isn't familiar.
Most people don't stop to consider this. To a chick, once they get outside the coop, the place looks totally different from out there, so no wonder they don't want any part of it. But resist the urge to chase them down and stuff them inside when night comes. It just makes for an awful experience for the chicks, and you, too.
The trick is to use the chicks' own instinct to want to go to bed, and to encourage them inside as they start to group together for this purpose. You'll know it's time when you hear them making their soft, barely audible bedtime trilling noises. That's your cue to get inside the coop with a small flashlight or plug in a night light. I like to show them I have their favorite treat and coax them inside with it.
It just takes a couple nights doing it this way, as opposed to over a week of the other more stressful way of stuffing them in, to teach them to go inside on their own.