ZIP Code 91786 · Upland, California
San Bernardino County · 20,352 counted · 4 districts
Each percentage here is a share of the 20,352 homes counted in ZIP Code 91786, not the chance that any one address is in that district. Enrollment follows the street: two houses on opposite sides of the same road can be in different districts, and only the district office can say which.
The districts named for the early grades in ZIP Code 91786, Upland, California are not the districts named for high school, and the set changes in both directions: one district arrives for high school that no elementary answer names, and another runs the early grades and stops. 4 districts hold the 20,352 homes counted here between them, and Upland Unified is the largest by homes. The largest share is high enough that one name is right for most of the homes counted and wrong for the other 1,635: 1,635 homes with Ontario-Montclair and Central Elementary.
Three districts share the early grades
3 districts hold a measurable share of ZIP Code 91786 at this level. Upland Unified is the largest with 18,717 homes; the smallest of them holds 195 homes. Ontario-Montclair and Central Elementary are named here for grade school and not for high school.
Every track below is 35 cells long and stands for all 20,352 homes counted in ZIP Code 91786, so one cell is 581 homes, rounded to the nearest whole cell. Cells lit solid are the homes one district holds, and the unlit cells are the homes held by the other districts in the same list.
- Upland Unified School District18,717 of 20,352 homes92%
- Ontario-Montclair School District1,440 of 20,352 homes7.1%
- Central Elementary School District195 of 20,352 homes1.0%
High school is split between two districts
2 districts hold a measurable share of ZIP Code 91786 at this level. Upland Unified is the largest with 18,717 homes; the smallest of them holds 1,635 homes. Chaffey Joint Union High is named here for high school and not for the early grades.
- Upland Unified School District18,717 of 20,352 homes92%
- Chaffey Joint Union High School District1,635 of 20,352 homes8.0%
The set of names changes in both directions
Chaffey Joint Union High is named for high school here and for no elementary grades, and Central Elementary and Ontario-Montclair run the early grades and no more. An address on the wrong street can therefore change district at the change of grade and land in a district that was never part of its elementary answer, while a neighbor two blocks away keeps one name the whole way through.
What one district name costs in 91786
A lookup that answers ZIP Code 91786 with one district name has to pick one of the names below and drop the rest. Measured against the 20,352 homes counted here, for the early grades it is wrong for 1,635 homes and for high school it is wrong for 1,635 homes. That is the whole difference between this page and a one-line answer: the same federal file, read to the end instead of to the first row.
The districts that reach into 91786
The districts named above are not alike in size or in reach. Chaffey Joint Union High touches 18 ZIP Code areas in all and holds 1,635 homes inside this one; Central Elementary touches 2 areas. Not one of them is ever the only district in a ZIP Code area anywhere in the country: every postal area they touch, they share with somebody.
- Upland Unified School District18,717 of 20,352 here · 6 ZIP areas in all
- Chaffey Joint Union High School District1,635 of 20,352 here · 18 ZIP areas in all
- Ontario-Montclair School District1,440 of 20,352 here · 7 ZIP areas in all
- Central Elementary School District195 of 20,352 here · 2 ZIP areas in all
Where Upland Unified goes from here
Upland Unified School District runs kindergarten through grade 12, and it is the only school district serving 0 of the 6 ZIP Code areas it touches, shares 3 more with neighbors, and holds under half a percent of the homes in the remaining 3. Inside its own boundary it holds 28,187 homes over 25 square miles; the part of it counted in ZIP Code 91786 is 18,717 of those. The district it shares the most postal ground with is Chaffey Joint Union High School District, across 3 ZIP Code areas. Its thinnest measured foothold is elsewhere: in ZIP Code area 91759 it holds 3 of 326 homes, or 0.9% of them.
How 91786 compares in California
Across California the boundary file names more than one district in 996 of the 1,788 ZIP Code areas it names a district for, 56% of them, and 3 areas in the state have no high school district named for part of their homes. Counting the districts named at either level, 150 areas in California name more than this ZIP Code does and 1,489 name fewer. Nationally more than one district is named in 53% of 33,555 areas.
Look up 91786 again, or look up another ZIP Code
The lookup holds every ZIP Code area in the country with homes in it, including the ones with no page of their own. Opening it at 91786 recomputes the same 20,352 homes from the same snapshot, and typing five other digits answers for somewhere else. No server is asked for the answer: the whole index travels with the lookup page itself.
What to do next
Ask the district office to confirm your street address. A district settles that question on its own site: look for a school locator, a find my school tool, or an attendance zone map. Where there is none, ask the office itself.
A ZIP Code is a set of mail delivery routes, not a boundary: 1,635 of the 20,352 homes counted in 91786 sit outside the district holding the most of them, and the line between the two runs along streets rather than around the postal area.
This site links to no district website. None of the federal files it is built from publishes one, and a guessed address is worse than none. It is the district office, not a search engine, that settles an address.
What this site can hand you instead:
If a house purchase depends on the answer, ask the district itself for written confirmation of that exact address. A listing is not a district record, and neither is this page.
What this cannot tell you
The homes were counted in the 2020 Census and the district lines are the 2026 boundary file. Nothing on this page adjusts one to the other. Where houses have been built or cleared since the count, a share here describes the place as it was counted rather than as it stands today, and in the fastest-growing ZIP Code areas that gap is the largest single source of error on this site.
A share on this page is a share of the homes in the ZIP Code area, not a probability for any particular address. Enrollment is decided by street address, and a district may run magnet, charter or choice programs that ignore the boundary entirely. If a decision depends on the answer, the district office is the only authority; this page shows what the federal boundary files say and when they were published.
A district boundary is not a school attendance zone. This site never says which school an address is assigned to: no current national dataset of attendance zones exists, and the district draws them itself. Nor is anything here endorsed or certified by the Census Bureau; we use their published files, and that is the whole of the relationship.
A ZIP Code is a set of mail delivery routes, not an area. What is mapped here is the Census Bureau's ZIP Code Tabulation Area, the closest published approximation to it. The two are not identical, and a handful of ZIP Codes used only for post office boxes or single buildings have no tabulation area at all.
Where these numbers come from
School district boundaries come from the Census Bureau's Census Geographic Relationship File, current 2026 vintage, which assigns every census block to a unified district or to an elementary and a secondary district. Homes and residents in each block come from the 2020 Census Redistricting Data (PL 94-171), H1_001 and P1_001. The ZIP Code areas come from the same Geographic Relationship File, block to ZIP Code Tabulation Area. District names and grade ranges come from the Census Gazetteer 2025, with 2020 for districts no longer listed.
The place name printed beside a ZIP Code comes from the Census 2020 ZIP Code Tabulation Area relationship files: place, county subdivision and county, taken 2026-09-06. It is a label rather than a measurement: the Census Bureau does not publish which post office a ZIP Code belongs to, so the place named is the one covering the most land inside the area, not the city the Postal Service prints on an envelope.
Everything else on this page — the shares, the counts of districts per ZIP, the comparison between the two grade bands, the rankings — is computed here from those files. The source publishes none of it. Snapshot taken 2026-09-03.