In little more than 10 years, enrollment had once again outgrown the facility. The closing of St. Joseph Seminary would add to the student body and in 1963, through the generosity of Mr. and Mrs.Romy Hammes, construction began on the rectangle addition to the circular building. In the 1964-65 school year, the new addition was opened, and the name changed to Bishop McNamara High School in honor of the first bishop of the Joliet diocese who had been instrumental in the central school’s development.
The Clerics of St. Viator administered the school until 1981, when, because of a growing shortage of priests, they had to discontinue their commitment. However, Viatorian priest, Father Erwin Savela, was hired as principal of Bishop McNamara High School and continued in that position until 1988. Mr. David Raiche was principal for one year, and then in 1990, the Order of St. Augustine assumed administration of the school. After 10 years, once again because of the decreasing number of priests available, the Augustinians ended their contract with Bishop McNamara High School and Mr. James Laurenti was named principal.