The Sisters of the Holy Child Jesus have also founded schools in England, Ireland, France, Nigeria, and Ghana.

The Provincial Council of the Society of the Holy Jesus responded to a need identified by the Bishop of Newark for a Catholic School for girls.

A stable, located where Connelly Hall now stands, provided gym and classroom space for the Junior School.

In 2004, Oak Knoll completed construction of athletic fields, located 5 miles (8.0 km) away in Chatham Township.

For students in grades 9-12, Oak Knoll offers 15 varsity and seven junior varsity competitive programs including: cross country, field hockey, soccer, tennis, volleyball, basketball, indoor track, ice hockey, sailing, fencing, swimming, lacrosse, softball, spring track, and golf.

[3] For students in grades 7 and 8, Oak Knoll offers: soccer, field hockey, cross country, basketball, lacrosse and non-competitive tennis.

[15] In 2007, the team won the North I, Group I state sectional championship with a 4–1 win over Pompton Lakes High School in the tournament final.

[17] In a repeat of the previous year's final, the 2015 team beat Bishop Eustace by a score of 4-2 in the championship game to win the Non-Public state title.

[21] The girls' lacrosse team won the 2005 North B state championship with an 8–4 win over Mountain Lakes High School.

[25] The girls' ice hockey team won the Union County Championship in 2020, the first year of the competition, with a 5–0 win against Summit High School.