Probably a considerable factor in "how high" is the breed of chickens you have. My polish fly quite well and like to be as high up as they can possibly get. The large fowl Cochin's seem content at 18 inches. And they still sound like bricks hitting the floor when they dismount in the morning.
I'm surprised by how often I am surprised : )) by what I observe when I take the time to just hunker down and watch. Enough room between the perch and the wall so no one has to brush the wall with tails or heads? Oops. Are they hitting their wings on the ceiling? Oops again. If they need to fly down, any obstacles on the way down? Stay awhile and watch to see how the adults maneuver in their coop. What worked for chicks isn't going to work for very long and I have been a little behind every once in awhile in enlarging and expanding their interior space.
I ended a lot ( but not all ) of the pushing and shoving that goes on at roost time by having roosts at only one height. I like the idea of the parallel rail that they can hop onto and use to access spots along the roost. Having to fly onto a roost is massively disruptive to everybody. I haven't made that change yet though.
Possibly other people have more talented fliers! LOL Roost placement has been no simple matter in MY coops.