Thornton High School

Thornton High School is a large, traditional high school in Thornton, Colorado, serving approximately 1,439 students in grades 9–12 as part of Adams 12 Five Star Schools. The district ranks solidly mid-range among Colorado districts, but Thornton High School consistently ranks among the lowest-performing high schools in the state — most recently placing in the 2nd percentile (330th out of 338) with zero stars. Over the past decade, the school has never ranked above the 19th percentile, and recent years show a downward trend.

Academic proficiency is far below district and state averages. Only 18% of 11th graders were proficient in SAT Reading/Writing (versus 55% district and 60% state), and just 6% were proficient in SAT Math (versus 33% district and 32% state). Math proficiency sits in the single digits across nearly all grade levels, and science follows the same pattern, with only 10.5% of 11th graders proficient on the state CMAS test. Chronic absenteeism is a major concern, affecting 58.2% of students in 2024–2025 — nearly double the district rate of 32.2% and more than double the state rate of 28.4%. On a more positive note, the graduation rate improved to 81.9%, up from 76.8% the prior year, though it still trails the district (85.8%) and state (85.6%) averages.

What makes Thornton's results especially striking is that nearby schools with similar demographics do better. Northglenn High School, just 1.2 miles away in the same district, has nearly identical poverty levels yet achieved a 14th percentile state rank, 33% SAT Reading proficiency, an 89% graduation rate, and a 1.0% dropout rate — compared to Thornton's 2nd percentile, 18% reading proficiency, 81.9% graduation, and 2.7% dropout rate. Several Mapleton School District No. 1 schools, including Academy High School, Mapleton Expeditionary School of the Arts, and Mapleton Early Career Preparation, also outperform Thornton on graduation and test scores despite their district ranking lower overall. Every student subgroup at Thornton — female, male, Hispanic, White, Asian, low-income, English learners, and special education students — performs in the bottom 10th percentile statewide. These patterns point to systemic challenges around attendance, instruction, and student support that require urgent attention.