Washington Township was created by an Act of the New Jersey Legislature on April 13, 1840, from the territories between the Hackensack River and Saddle River that had been part of Harrington Township. At the time of its creation, the township encompassed an area of 19,525 acres (79.01 km2), more than 30 square miles (78 km2). Growth in the area exploded after the Civil War with the completion of the New Jersey and New York Railway through the Pascack Valley, as communities were established near the railroad's stations.
Public school students in kindergarten through twelfth grade attend the Westwood Regional School District, a comprehensive regional school district serving students from both the Township of Washington and Westwood Borough. The district is the county's only regional district serving grades K-12. Schools in the district (with 2017–18 enrollment data from the National Center for Education Statistics) are Berkeley Avenue Elementary School (292 students; in grades K-5), Brookside Elementary School (419; K-5), Jessie F. George Elementary School (258; K-5), Washington Elementary School (296; K-5), Westwood Regional Middle School (419; 6-7) and Westwood Regional High School (1,111; 8-12)
Public school students from the township, and all of Bergen County, are eligible to attend the secondary education programs offered by the Bergen County Technical Schools, which include the Bergen County Academies in Hackensack, and the Bergen Tech campus in Teterboro or Bergen Tech campus in Paramus. The district offers programs on a shared-time or full-time basis, with admission based on a selective application process and tuition covered by the student's home school district.
Immaculate Heart Academy is a parochial, college preparatory, all-girls Catholic high school located on Van Emburgh Avenue, operating under the auspices of the Roman Catholic Archdiocese of Newark. The school was founded in 1960 as the first all-girls school operated by the Newark Archdiocese.