Okay then. Chickens nearly full grown require a different approach when integrating than small babies where the panic room method works so well.
Even though nearly three-month old chicks are getting to a size where they don't appear to be so vulnerable, they still lack rank, confidence, and experience that help them cope with their places in the pecking order.
They need a little help. One thing I do for my chicks as they are getting larger but still lack the self confidence to buck the pecking order to get the essentials they need is to install a vertical refuge. This can be a shelf in the run or something as homely as an old card table or patio table.
This is where I place their food and water. I show them once where it is, and they are quick to see it as a place where they can escape the pressure of trying to compete at the flock feeder down low. They also find it a comfortable and secure place to relax and nap.
As for going into the coop at night, they need your help there, too. First, see to it that there are enough roosting perches where the chicks don't need to try to crowd in with the adults, risking being shoved off the perch. Usually, the adults will have their favorite spots on the perches, so you need to encourage the youngsters to roost at the opposite end, or even make a temporary perch down low for them.
To teach them to go inside at night, wait until the adults have roosted. Younger chickens naturally will wait to go in last, even as they've reached maturity. It helps to have a light inside the coop if it happens to be dim in there, making it darker inside than out. Chicks need to see that where they're going is safe.
I will give them a gentle shove to get them to go in or I will get inside and call them in. Then I will place them on the perch where they will feel safe from the adults. If they are agitated, I will place my hand lightly on their heads, exerting soft downward pressure while making a shh-ing sound. This comforts and relaxes them.
It only takes a few nights of this and they will be going in and roosting on their own. Of course, if there's an adult bully, you will need to be prepared to deal with that. I have a fly swatter handy that I use to thrust in between an adult bully and her target. Believe me, this sends a message pretty quickly, and all I need to do is brandish the swatter and the bully backs right down.