Montclair Academy was founded in 1887 with 32 male students. By 1891, the school had expanded to include living quarters and was renamed the Montclair Military Academy. Following World War I, the school's name reverted to Montclair Academy, with enrollment reaching 300 students by 1925. In 1906, Miss Waring's School and Studio opened in Montclair with 46 female students. The school was renamed the Kimberley School in 1909 after headmistress Mary Kimberley Waring, and was run privately for more than 30 years before incorporating as a nonprofit institution in 1941.
Finally, in 1925, a group of Montclair parents formed the coeducational Brookside School for 30 students in grades K-6. In 1968, Montclair Academy and the Kimberley School began to offer cross-registration in some classes, shared events and theatrical production. The final step was taken in 1974 when all three schools were combined to create the Montclair Kimberley Academy.
Today, the college preparatory school offers grades K-12 and is, according to the website, one of the largest independent day schools in New Jersey with an enrollment of nearly 1,000 students.