Union school district

In some U.S. states, a union school district or union high school district is a school district that has been established by the consolidation of "two or more school districts situated in the same county". A Joint union school district is similar, but the component districts are "situated wholly or in part in different counties". A union school district is distinctive from a unified school district in a union school district generally does not include or operate primary or grade schools and high schools, whereas a unified district generally includes and operates both types of schools. (Vermont has a different distinction, as explained below.)

In Arizona, a union high school district is generally one that includes and operates high schools. Sometimes the name is derived from the name of the first school that was opened, using the word "Union" in its full name. Examples include the Casa Grande Union High School District (the Union school still uses the full name), the Phoenix Union High School District, the Glendale Union High School District, and the Tempe Union High School District. Some special union high school districts — such the Santa Cruz Valley Union High School District — include and operate only one school.

The California Education Code states that "A high school district, other than a city high school district, comprising two or more elementary school districts lying wholly in the same county is a union high school district, and such designation shall be part of its name."

In Vermont, a union school district "is established when two or more school districts agree to join together to own, construct, or operate schools." A union school district is a unified school district if the town school districts have been abolished.

There are also several school districts which simply have the name "Union School District" or similar constructions:

...
Wikipedia