Heck Tate and Mr. Underwood are both on Atticus' side.
We especially see this when Heck Tate does not make an arrest in Bob Ewell's death.
He changed his name from James Gatz to Jay Gatsby when he was seventeen, and this is because he wanted to run away from his unfortunate life as James Gatz and start another one as he met Dan Cody in the Lake Superior.
Yes they should! Most of you claiming that the "juvenile brain" is underdeveloped is on orthodox. The normal human brain doesn't stop completely developing until the age of 22. Does that mean that we should excuse anyone under the age of 22 of their crimes? I think not. Also, if a juvenile were to come into your home, murder your whole family just for the thrill of it, your decision on juveniles not staying in prison for life, would change.