Good discipline and a focus on the basics are important, but I’d also like to see the teaching strategies used and how the administration supports good teaching methodology and interacts with parents.
You might want to google "high-flying schools" - these are schools with high achievement even though they have high poverty and/or minority populations. I've seen a couple of books that give the common characteristics of these high-flying schools.
There are also some people who say the methodology of identifying the schools was flawed and overestimates the number of such schools. Probably a bit of ideology in both viewpoints.