High quality schools are defined as the top 20 percent of schools within each school level (elementary, middle and high) using the Colorado Department of Education's school performance framework. Specifically, the overall percent of points earned on the 2019 School Performance Framework was used to identify the high quality schools.
The "Access Score" is measured using two factors:
1) the share of relevant student-aged children enrolled at a high quality school; and
2) the driving time to the nearest high quality school.
The first factor is determined by identifying intersecting school district and zip code geographies. For each school district, the following calculations were made: 1) the number of students enrolled at high quality schools within the district; and 2) the estimated number of relevant student-aged children residing in the district. This is done serparately for each level: elementary, middle, and high so that the calculation for high quality elementary schools uses the number of students enrolled only at high quality elementary schools and the number of children in a school district between the ages of 5 and 9. For each zip code, the total high quality school enrollment of all intersecting school districts is divided by the estimated count of students that are age-eligible for those schools districts.
Student enrollment data were obtained from the US Department of Education, National Center for Education Statistics, Common Core of Data (CCD) for the 2016-17 school year. Student-aged population data were obtained from the US Department of Education, National Center for Education Statistics, Education Demographic and Geographic Estimates (EDGE) for the 2016-17 school year.
For the second factor, school addresses were retrieved from the US Department of Education, National center for Education Statistics, Common Core of Data (CCD). The Google Maps Distance API was used to calculate the driving time from the centroid of each zip code to nearby high quality schools.
Each factor was individualy scored on a scale of 1 to 5 as follows:
| High Quality School Enrollment Proportion | Points | Driving Time | Points |
|---|---|---|---|
| .70+ | 5 | 0 to 10 minutes | 5 |
| .50 to .69 | 4 | 11 min. to 20 min. | 4 |
| .30 to .49 | 3 | 21 min. to 45 min. | 3 |
| .15 to .29 | 2 | 46 min. to 60 min. | 2 |
| Less than .15 | 1 | 61 min. + | 1 |
The factor scores were then combined to create the composite index score, with the first factor (high quality school enrollment) weighted at 60 percent and the second factor (driving time) weighted at 40 percent.