[1] He graduated from Cathedral High School and went on to attend the College of the Holy Cross, where he majored in political science, played end for the Holy Cross Crusaders football team, and was a member of the school's swim team.

[2] In 1950, while a senior at Holy Cross, Costello ran for one of the 18th Suffolk district seats in the Massachusetts House of Representatives.

The 18th Suffolk district consisted of Costello's home neighborhood of Jamaica Plain, as well as Forest Hills and Roslindale.

During the final month of the primary race, he practiced football in the afternoon and campaigned at night.

During his first year in the legislature, Costello attended class during the day, worked at the state house during the afternoon, and studied at night.