The top 15 campuses in the rankings include magnet schools, small campuses offering specialized programs, and charter schools. Two of the top five schools are part of the BASIS charter school network in Arizona, which offers an intensive curriculum designed to be comparable to international academic standards.
The news outlet's formula for determining the best campuses is a combination of overall school performance on statewide proficiency tests, factoring in considerations for populations of disadvantaged students who typically score lower on such assessments. Schools that did well enough on those factors were then evaluated for "college readiness," using student achievement on Advanced Placement and International Baccalaureate (IB) exams. (Because the data is self-reported by schools and states to a federal database, errors can occur -- which was the case for a number of campuses in last year's rankings.)
It's important to note that the rankings are a snapshot of a school's performance, rather than a definitive judgement. However, they do shine a light on campuses that are exceeding achievement benchmarks often with challenging student populations.