Founded in 1955, the district now encompasses residents of the Census-Designated Places of Holbrook, Holtsville and Farmingville, as well as some parts of the Incorporated Village of Lake Grove and the CDPs of Lake Ronkonkoma, Ronkonkoma, Nesconset, Bohemia and Bayport.

[2] As of 2011, its district office is located in Lake Ronkonkoma at Samoset Middle School.

Sachem East was built as a 9-12 facility for students in the southern and eastern portions of the district.

Sachem East is also the second largest suburban high school in New York state.

[5] On September 16, 2015, the Sachem School District Board of Education voted to cut custodial staff, athletics, clubs, and other extracurricular activities in order to reallocate $2.5 million for Special Education services and worker compensation costs.