Large, traditional urban high schools are among the most difficult education environments in the United States. These schools, which serve a high percentage of the Black and Latino students in the United States, often have low academic performance, high dropout rates, high teacher and school leader turnover, and inexperienced teachers. They often exist within contexts of high poverty, high family mobility, high unemployment, and low social capital. However, because they serve such a high percentage of students nationally, academic success at these schools is an equity issue with major national economic and social wellbeing implications. As a result, there have been many efforts to reform these urban high schools or whole urban districts. Despite some exceptions, particularly in small schools that serve a small percentage of students, the success of these reforms has been limited. This is the report of a qualitative study of teachers', school leaders', and students' perceptions of three large, traditional urban Texas high schools that were exhibiting the most success in math and science when compared to similar large, traditional urban Texas high schools after statistically controlling for the challenges each school faced. The 3 themes that emerged to describe the similarities among these three schools were leadership, equity orientation, and instructional focus. However, the highlight of the results was long lasting, stable teachers' professional communities composed of diverse, experienced teachers with particularly strong equity orientations. (Contains 1 figure, 3 footnotes and 2 tables.)