Hillside School opened its doors as a grade 3–6 school in September of 1962. It is situated on 20 acres of land that was sold to the district for $1.00. Mr. Walter Kritzberger was the first principal. It was a 3-6 school until June of 1964. In September of 1964, Van Holten was opened as the new K-4 school. Hillside then became a middle school housing 5th, 6th, 7th and 8th grade students. All the third and fourth grade students and teachers were transferred to Van Holten.
The next major transition for Hillside School revolved around the closing of Washington School in 1979. A large number of students and faculty from Washington School were transferred to Hillside. Mr. Kritzberger retired, and Mr. Wilson Bethard, who was the principal of Washington School, became the new principal of Hillside. The fifth graders were transferred out of Hillside, now making Hillside a Grades 6, 7 and 8 school. It was at this time that Hillside piloted Team Teaching.
Hillside remained a middle school until June of 1995. In September of 1995, it was converted to an intermediate school, housing grades 4, 5 and 6 while Bridgewater High School East was transformed into a middle school. Principal Bethard was transferred to the new middle school, and Mrs. Teresa Pennington was appointed the principal of Hillside. It was also at this time that the sixth graders re-joined the seventh and eighth graders at the middle school. Over the summer of 2014, Mrs. Pennington retired and Mr. William Ferry took over as Principal.
In 2001, Jane Goodall visited Hillside School to attend our annual Forest Fest. She again came to Hillside School in 2004 to designate it as not only the first free-standing school, but also the first elementary school, to have the distinction of being a Roots & Shoots School in the U.S.
Hillside remained an intermediate school housing grades 4 and 5 until September, 2006, when it was converted to a Grade 5 and 6 school. With this conversion, came a new 3-story addition that included project/science rooms, small group rooms, music rooms, a computer lab and an auxiliary gym. Hillside continues its participation as a Roots and Shoots school today.