Ground was broken at the site of Holy Trinity School in October 1952, and construction was begun in May 1953. On Sunday, June 20, 1954, the official dedication of the school was held with the Most Reverend Francis P. Keough, DD, presiding and the Rev. Michael W. Hyle as featured speaker. Opening day, September 7, 1954, saw a student enrollment of 504 and a staff of six Sisters of Notre Dame de Namur assisted by three lay teachers.

With the division of Holy Trinity Parish into four separate and independent parishes, the parochial affiliation of the school was no longer practical. In July, 1973, the Northern Anne Arundel Regional Catholic School was organized under the Archdiocesan Board of Education, using the facilities of the Holy Trinity school-convent education complex and serving the parishes of Good Shepherd (Glen Burnie), Crucifixion (Glen Burnie), St. Bernadette (Severn), Our Lady of the Fields (Millersville), and St. Joseph (Odenton), as well as Holy Trinity (Glen Burnie). During the 1977-78 school year, St. Elizabeth Ann Seton (Crofton) became the seventh member of the Regional School parishes. During the 1991-92 school year, Our Lady of the Chesapeake (Pasadena), became the eighth member of the Regional School parishes. In 1994-95 St. Lawrence Martyr (Jessup), became our ninth parish.

The parishes of St. Elizabeth Ann Seton, St. Joseph, and Our Lady of the Fields disincorporated with Monsignor Slade Catholic School in 2001 to form a new parochial school which serves families in the southern part of Anne Arundel County.

Renamed the Arthur Slade Regional School by Lawrence Cardinal Shehan at dedicatory ceremonies on February 24, 1974, the school continues its fine tradition of service to the people of Anne Arundel County, providing a religious-oriented education for kindergarten and grades 1 through 8 in the primary, intermediate and middle school levels. Since 1975, a state-approved Edu-Care Center has functioned providing services for 3-4 year olds. The expansion of the Edu-Care center in the fall of 1994 brought the addition of a part-time nursery school program for children ages 2-4.

2004 marked the 50th Anniversary of the school and Slade is proud of its continuing reputation for academic excellence in Anne Arundel County. Since opening day in 1954, enrollment has increased 75% to almost 900 students and the faculty has grown more than four-fold to nearly 40 teachers. A major renovation of the school auditorium was completed in 2004 in honor of the 50th Anniversary. The school was re-named Monsignor Slade Catholic School in 2004 to honor the priestly ministry of its founder.

Monsignor Slade Catholic School stands today as a living tribute to the faith and foresight of its founder, Father Arthur C. Slade, pastor of Holy Trinity Parish from 1946 to 1968. A vision of the necessity of Catholic education for the children of his parish was a compelling force motivating his life. Monsignor Slade died on November 12, 1971. The school personnel and parent communities have striven to develop a quality, religious-oriented program faithful to the legacy passed on by Monsignor Slade.