Best Public Schools in Zip Code 83321

Zip code 83321 contains just one school, Castleford School, an alternative PK-12 institution in the Castleford District serving 274 students in a small rural Idaho community.

Castleford School is a high-poverty school with 71.53% of students eligible for free or reduced-price lunch, yet it maintains a graduation rate of 82.5% that exactly matches the state average. The school also posts a chronic absenteeism rate of 12.3%, below the state's 13.8%, and enjoys a favorable 13:1 student-teacher ratio that supports individualized attention. On the 2025-2026 ISAT assessments, the school trails the state in all subjects across all grades combined: math proficiency is 40.4% versus the state's 43.1%, science is 36.4% versus 42.7%, and English Language Arts is 43.1% versus 54.0%. However, the school is improving, showing year-over-year gains in math (+3.2 points), science (+8.3 points), and ELA (+4.4 points).

The most striking finding is Castleford School's exceptional performance on End of Course exams, where older students dramatically outperform state averages: Science EOC proficiency is 62.5% versus the state's 41.2%, a 21.3-point advantage; ELA EOC is 70.8% versus 61.3%, a 9.5-point advantage; and Math EOC is 41.7% versus 33.1%, an 8.6-point advantage. By contrast, the school struggles in middle-grade ELA, with 4th grade at 33.3% (16.9 points below state), 5th grade at 40.0% (15.2 points below), and 7th grade at 42.3% (14.5 points below). Math results are mixed, with strong showings in 4th grade (+2.0), 6th grade (+7.5), and EOC (+8.6), but a notable weakness in 7th grade (12.8 points below). Since Castleford School is the only school in the Castleford District, district-level metrics are identical to school-level metrics, making the state average the most meaningful benchmark. Per-student spending of $9,860 dates from 2018-2019, so current funding levels are unknown.