The top reported proficiency rate is 65% in Math. The lowest is 53% in Science.
Original Research by School Decision on Castlio Elem.
Castlio Elementary serves kindergarten through fifth grade in the Francis Howell R-III school district, located in St. Charles. The city itself is a historic northwestern suburb of St. Louis, with a walkable downtown core along the Missouri River and more car-dependent residential and commercial development along the Interstate 70 corridor beyond that district. The school sits in a part of the community where home values and rents run well above state and national medians, and the typical household here has a fairly high income. A modest share of students qualify for free or reduced-price lunch, a sign of a broadly affluent attendance zone with some economic diversity.
The school is a regular public school, not a charter or magnet. It is a large elementary school for its grade span, with enrollment distributed consistently across grades kindergarten through fifth. The student body is predominantly white, with smaller Asian, Hispanic, and Black populations and a modest number of students identifying as two or more races. Data on special education and English learner enrollment was not available in the source material.
On state assessments, Castlio’s performance stands out. In both math and English language arts, the school’s proficiency rates sit above the midpoint among districts in St. Charles County, and its overall proficiency index places it in the top quartile relative to other districts in the county. That index, a mean of reported rates across tested subjects and grades, comes in higher than the county median. In specific terms, math proficiency was strong across all three tested grades, with the fourth-grade cohort performing particularly well. English language arts results followed a similar pattern, with fourth graders again showing the highest proficiency. Science, tested only in fifth grade, showed a lower proficiency rate relative to math and reading at that same grade level, a soft spot a parent may want to ask the school about.
Because Castlio serves only elementary grades, there is no graduation rate to report. That is a function of the school’s grade band, not a missing metric.
The district context matters for families considering this school. The Francis Howell board has made several news-making policy changes in recent years, all publicly reported. In 2024, voters approved a bond issue for capital improvements and safety upgrades. The same year, the board voted to restore abstinence-only sex education and approved a policy restricting classroom displays to official U.S., Missouri, and district flags. In 2023, the district removed eight books from library shelves following complaints. These are lasting decisions that shape the curriculum and school culture, and they are worth factoring into any enrollment decision.
Castlio does not offer high school programs like Advanced Placement or career pathways, as those are beyond its grade scope. No information on discipline rates, chronic absenteeism, or staffing ratios was available in the source data.
Overall, this is a high-performing elementary school in an affluent, growing suburb that sits within a district that has made deliberate and debated choices about its policies and curriculum. The academic foundation for students through fifth grade appears quite solid, particularly in math and reading, with some room for attention in elementary science. Families who value a clear track record of test results and a district that is actively defining its values may find Castlio a strong fit. Those seeking more information on special populations support or classroom climate would need to contact the school directly, as those details were not provided in the data reviewed here.
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