The late 1960s and early 1970s was marked by the merger between the two schools.
The merger was brought about by many factors, including the sense of shared history and goals between the two schools, common activities, plus survey research showing that 94% of students in northeastern secondary schools wished for coeducation.
The times "favored coeducation"; in 1968, 53 colleges and universities either became coeducational or began coordinate instruction.
While Phillips Academy "held the cards" regarding whether the two schools should merge, there was a "crasser impetus" from admissions statistics, as Phillips was increasingly being turned down by applicants preferring newly-coeducational competitors such as St. Paul's, Taft, Northfield-Mount Hermon, and Exeter.
Many committee meetings, including discussions between administrators and teachers, happened over a sixteen-month period.
The Phillips headmaster, John Kemper, who had kinship ties with women graduates of Abbot, felt a merger was "practical, ethical, and educationally sound", although several times the Phillips Board of Trustees refused to sanction a merger.
The school merged with Phillips Academy on June 28, 1973.
Many Abbot traditions were included in the combined school, such as having a designated weekend in the fall for parents to visit.

Parents’ Weekend was Abbot’s response to formalize parent visits to the school.
In the past, parents would visit the school on many different occasions.
The event created one specific weekend for all parents to visit.

— Tim Sprattler, 2009
After the merger, $1 million of Abbot's endowment became the basis for the Abbot Academy Association, which funds various educational programs and projects submitted by students, faculty, and staff.
Since the first Abbot Grant was awarded in the fall of 1973, nearly 2000 Abbot Grant proposals have been submitted by students and members of the faculty, staff and administration of Phillips Academy.
The Abbot Academy Association has funded more than 1400 of these proposals with grants totaling $9,400,000.
 In 2014, the Abbot Academy Association's endowment had grown to $10 million.
The late 1960s and early 1970s was marked by the merger between the two schools. The merger was brought about by many factors, including the sense of shared history and goals between the two schools, common activities, plus survey research showing that 94% of students in northeastern secondary schools wished for coeducation. The times "favored coeducation"; in 1968, 53 colleges and universities either became coeducational or began coordinate instruction. While Phillips Academy "held the cards" regarding whether the two schools should merge, there was a "crasser impetus" from admissions statistics, as Phillips was increasingly being turned down by applicants preferring newly-coeducational competitors such as St. Paul's, Taft, Northfield-Mount Hermon, and Exeter. Many committee meetings, including discussions between administrators and teachers, happened over a sixteen-month period. The Phillips headmaster, John Kemper, who had kinship ties with women graduates of Abbot, felt a merger was "practical, ethical, and educationally sound", although several times the Phillips Board of Trustees refused to sanction a merger. The school merged with Phillips Academy on June 28, 1973. Many Abbot traditions were included in the combined school, such as having a designated weekend in the fall for parents to visit.
Parents’ Weekend was Abbot’s response to formalize parent visits to the school. In the past, parents would visit the school on many different occasions. The event created one specific weekend for all parents to visit.
— Tim Sprattler, 2009
After the merger, $1 million of Abbot's endowment became the basis for the Abbot Academy Association, which funds various educational programs and projects submitted by students, faculty, and staff. Since the first Abbot Grant was awarded in the fall of 1973, nearly 2000 Abbot Grant proposals have been submitted by students and members of the faculty, staff and administration of Phillips Academy. The Abbot Academy Association has funded more than 1400 of these proposals with grants totaling $9,400,000.  In 2014, the Abbot Academy Association's endowment had grown to $10 million.
Abbot Academy