Now, as someone who just came out of a school that's an actual success story rather than a failure, I can sum up the general consensus on school schedule from the students, teachers and administrators, with a quote from one of my history teachers who just retired,
"8 to 6, Monday through Thursday. Push more homework towards the weekends, if you still need it."
Now, longer hours works, for only one reason. Most teachers need at least an hour a class in order to do anything really effectively, especially as high school goes on. I had a geopolitics teacher who loathed a 41 minute class, because he felt that geopolitics needed to be divided into 2-hour lectures, and he couldn't have anywhere close to 2 hours for each lesson. He has that time, he can probably reach out to more people - granted, most students still met the curriculum and are quite able in the art, but he felt he could improve, and if he taught at a zone school, the longer lesson times would definitely help more. My friends actually felt they weren't staying in school long enough, and that 3:30 was a very early time to be leaving. About 40% of the school routinely stayed after the last bell for some after-school group, crew, practice session, the like.
In addition to this, after-school activities should last until 9 or 10 PM, or even better, be pushed to Fridays. Days of relaxation, still within an academic sphere, but it would essentially be the students' day to do something that benefits their school or their community. Of course, this is optional.
The reason that Friday is off is very simply, really; teachers need their rest too. The biggest complaint I heard from them was that they never got the time to work their lesson plans. Having an extended school day, 5 days a week is just going to kill the teachers more than the students.
It's not a compromise, it's the only way it can work.