R5 By the Numbers: Our Sortable High School Data Chart

On page 96, we give you some data to help evaluate your local high school. Here, we explain those numbers.
Median Household Income: Since district-specific income data is not available (thanks in part to Westchester’s labyrinthine setup of overlapping municipalities), we’ve used the income figure for the zip code in which each high school physically resides—or the village when the zip code’s income is not representative of the district.
Percentage of Students in Poverty: The percentages are for school-age children (5 to 17) in each high school’s district, derived from 2010 figures collected for the Census Bureau’s Small Area Income and Poverty Estimates (SAIPE) program.
Gross Per Pupil Expenditures: How much the school spends to educate each child.
Mean SAT Scores: The SAT is a popular standardized college admissions test.
Aspirational Performance Measure: Conceived and calculated by the New York State Department of Education, the APM rate indicates the percentage of students who graduated with a local, Regents, or Regents with Advanced Designation diploma and earned a score of 75 or greater on their English Regents examination and an 80 or better on a math Regents exam.
Teachers with MA or PhD: The percentage of faculty that has advanced degrees. Presumably, the better educated a teacher is, the more knowledge he/she can impart.
Average Class Size: It is generally agreed that smaller classes are more conducive to more learning.
Guidance Counselor-to-Student Ratio: How many guidance counselors there are dedicated to how many students.
Students in Extracurricular Programs: Some studies have shown a direct correlation between involvement in extracurricular activities and higher grades.
Percentage of students taking AP/college-level courses: AP (Advanced Placement) and similar college-level classes (IB) are challenging; one way to judge how well a school engages its students is by how well it challenges them.
Four-Year Graduation Rate: The greater number of entering freshmen who graduate in a timely four years (as opposed to five or more, or not at all) can indicate that a school has kept its students engaged and involved.