The five campuses of Lancaster Mennonite School have a rich history. All were founded in response to a call to give parents an alternative to public schools where students could be taught in a Christ-centered environment. This movement led to the founding of Locust Grove Mennonite School in 1939 and New Danville Mennonite School in 1940. The Lancaster Conference of the Mennonite Church took a bit more time to meet a bigger challenge: the development of a Christian high school on the site of the former Yeates School in 1942. To better serve families in northwest Lancaster County, Lancaster Mennonite School then helped to start Kraybill Mennonite School in 1949. Years later, a parent association founded Hershey Christian School in 1995 to offer K-12 Christian education in southern Dauphin County and surrounding communities.
Whereas each of the Mennonite schools initially served mainly Mennonite students, persons from many denominations increasingly became part of the student body. Each campus eventually served a diversity of Christian families who appreciated an excellent education in a Christ-centered atmosphere that emphasized personal faith and discipleship.
Although each school was founded independently to meet the challenges of the 20th century, the challenges of the 21st century brought them all together to be one comprehensive PreK-12 school with five campuses. Sharing a common mission and values, the schools decided to work together as a system for the common good. New Danville merged with Lancaster in 2001, followed by Locust Grove in 2003 and Kraybill in 2006. On February 26, 2015, Hershey Christian School became Lancaster Mennonite School’s fifth campus.
In 2017 the Saint James School — An LM Early Childhood Education Program — was formed in conjunction with Saint James Episcopal Church, Lancaster.
- 1939: Locust Grove Mennonite School (now Locust Grove Campus) founded
- 1940: New Danville Mennonite School (now New Danville Campus) founded
- 1942: Lancaster Mennonite School founded
- 1949: Kraybill Mennonite School (now Kraybill Campus) founded in the Kraybill Meetinghouse with grades 1-10 in cooperation with Lancaster Mennonite School
- 1965: LMS builds a junior high building on the Kraybill campus
- 1970: Lancaster Mennonite School renamed Lancaster Mennonite High School to emphasize that it offered grades 9-12.
- 2000: Middle school (grades 6-8) started on the Lancaster Campus
- 2001: New Danville Mennonite School merges to form Lancaster Mennonite School, one K-12 school with two campuses
- 2003: Locust Grove Mennonite School (PreK-8) merges with Lancaster Mennonite School and becomes the Locust Grove Campus (PreK-8)
- 2006: Kraybill Mennonite School (K-8) merges with Lancaster Mennonite School and becomes the Kraybill Campus (PreK-8)
- 2015: Hershey Christian School (K-12)is acquired
- 2017: Saint James School — An LM Early Childhood Learning Center — is formed through a partnership of LM and Saint James Episcopal Church, Lancaster