ZIP Code 91766 · Pomona, California
Los Angeles County · 19,535 counted · 3 districts
Each percentage here is a share of the 19,535 homes counted in ZIP Code 91766, 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 91766, Pomona, California are not the districts named for high school, and the set changes in both directions: 1 district arrives for high school only, 1 runs the early grades and stops, and 1 serves both bands. 3 districts hold the 19,535 homes counted here between them, and Pomona 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 1,082: 1,077 homes with Ontario-Montclair and 5 homes in a district too small to name here.
The early grades are split between two districts
2 districts hold a measurable share of ZIP Code 91766 at this level. Pomona Unified is the largest with 18,453 homes; the smallest of them holds 1,077 homes. Ontario-Montclair is named here for grade school and not for high school.
Every track below is 35 cells long and stands for all 19,535 homes counted in ZIP Code 91766, so one cell is 558 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.
- Pomona Unified School District18,453 of 19,535 homes94%
- Ontario-Montclair School District1,077 of 19,535 homes5.5%
Below half a percent at the grade school level: Chino Valley Unified School District holds 5 homes, which is why it is counted under the list rather than inside it. A lookup that named it alongside the districts above would be listing a boundary crossing rather than an answer.
High school is split between two districts
2 districts hold a measurable share of ZIP Code 91766 at this level. Pomona Unified is the largest with 18,453 homes; the smallest of them holds 1,077 homes. Chaffey Joint Union High is named here for high school and not for the early grades.
- Pomona Unified School District18,453 of 19,535 homes94%
- Chaffey Joint Union High School District1,077 of 19,535 homes5.5%
Below half a percent at the high school level: Chino Valley Unified School District holds 5 homes, which is why it is counted under the list rather than inside it. A lookup that named it alongside the districts above would be listing a boundary crossing rather than an answer.
Have a street address?
A ZIP Code names every district that can serve the area; a street address settles which one serves a home. The Census Bureau geocoder takes an exact address and returns its school districts from the current boundary files, free and with no account.
Check an exact address with the Census Geocoder
Then confirm it with the district office. Each district named here, with its NCES district ID, website and phone:
- Pomona Unified School District NCES ID 0631320 pomona.k12.ca.us (909) 397-4800
- Chaffey Joint Union High School District NCES ID 0608160 cjuhsd.net (909) 988-8511
- Ontario-Montclair School District NCES ID 0628470 omsd.net (909) 459-2500
The set of names changes in both directions
Chaffey Joint Union High is named for high school here and for no elementary grades, and Ontario-Montclair runs 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 91766
A lookup that answers ZIP Code 91766 with one district name has to pick one of the names below and drop the rest. Measured against the 19,535 homes counted here, for the early grades it is wrong for 1,082 homes and for high school it is wrong for 1,082 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 91766
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 1,077 homes inside this one; Pomona Unified touches 7 areas. Pomona Unified is the only district in at least one ZIP Code area somewhere in the country, while Chaffey Joint Union High is never the only one anywhere: every postal area it touches, it shares.
- Pomona Unified School District18,453 of 19,535 here · 7 ZIP areas in all
- Chaffey Joint Union High School District1,077 of 19,535 here · 18 ZIP areas in all
- Ontario-Montclair School District1,077 of 19,535 here · 7 ZIP areas in all
Where Pomona Unified goes from here
Pomona Unified School District runs kindergarten through grade 12, and it is the only school district serving 1 of the 7 ZIP Code areas it touches, shares 4 more with neighbors, and holds under half a percent of the homes in the remaining 2. Inside its own boundary it holds 48,566 homes over 31 square miles; the part of it counted in ZIP Code 91766 is 18,453 of those. The district it shares the most postal ground with is Walnut Valley Unified School District, across 2 ZIP Code areas. Its thinnest measured foothold is elsewhere: in ZIP Code area 91789 it holds 252 of 13,515 homes, or 1.9% of them.
How 91766 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, 299 areas in California name more than this ZIP Code does and 1,208 name fewer. Nationally more than one district is named in 53% of 33,555 areas.
Look up 91766 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 91766 recomputes the same 19,535 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: look on its site for a school locator, a find my school tool or an attendance zone map, or call the office.
A ZIP Code is a set of mail delivery routes, not a boundary: 1,082 of the 19,535 homes counted in 91766 sit outside the district holding the most of them, and the line between the two runs along streets rather than around the postal area.
District websites and phone numbers here come from the NCES Common Core of Data directory, 2024-25 school year, filed under the same district ID as the Census boundary files. Where it lists no usable website, none is printed rather than guessed.
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.
Where these numbers come from
The homes were counted in the 2020 Census and the district lines are the 2026 boundary file, so a fast-growing area may have changed since; ZIP Codes here are the Census Bureau's ZIP Code Tabulation Areas; a share is a share of homes, not the chance that one address is in a district; and a district is not a school attendance zone. Every source, file and caveat is on the method page.