Millbrook School is a private, coeducational preparatory school located in Dutchess County, New York, USA. It is governed by a self-perpetuating Board of Trustees, and is accredited by the New York State Association of Independent Schools and the Board of Regents of the State University of New York. Institutional memberships include the Cum Laude Society, the Secondary School Admission Test Board, the National Association of Independent Schools, the New York State Association of Independent Schools, the Council for Advancement and Support of Education, and A Better Chance. As of 2009, the school's endowment stood at approximately $20 million; relatively modest in comparison to other private schools in the region.
 
Millbrook School was founded in 1931 by Edward Pulling. Pulling was a graduate of both Princeton University and Cambridge University, and he taught at both Groton School and Avon Old Farms as well as private schools in the United Kingdom. While at Avon, Pulling began to think of creating his own school. His philosophy for a school was heavily influenced by the traditional setting he experienced at Groton and in the UK as well as the progressive ideology that Avon possessed. After searching for suitable grounds to house the school — including an offer from then Governor Franklin D. Rooseveltto build in Hyde Park, New York — Pulling and his wife decided on the Stephenson farm just 5 miles (8 km) outside Millbrook, NY.
After the purchase of the property Pulling drafted his first board of trustees, which included Endicott Peabody Sr., who was headmaster at Groton, and Henry Harkness Flagler, who became the first President of the Board of Trustees. With the generous support of the Flagler family and Pulling's father-in-law Russell Leffingwell the campus increased from the original farm buildings to include a vast majority of the current campus infrastructure.
While the campus has many traditional values what makes Millbrook unique is the progressive mission that the school embodies. The school motto is "Non Sibi Sed Cunctis" Latin for "Not for One's Self but for All" and this is incorporated in every facet of school life, most notably in the Community Service Program. Edward Pulling wanted every student who attended Millbrook to contribute something to the maintenance and upkeep of the school as well as contributing something to the surrounding community. Originally functions performed by students included fire safety, running the post office, growing food, dishwashing, helping to maintain the zoo (zooies) and a variety of other duties to help the school. By the time WWII began Millbrook used its community service program to help the war effort. In the subsequent years the community service program has changed considerably to encompass a much larger variety of programs that are much more specialized. They run the gamut from tour guides to an outreach program to head waiters (in charge of the dishwashers) to peer counselors that help students deal with the stressful life of boarding school. Every student is required to participate in a community service all four years of their stay at Millbrook and many keep with the same service all four years.
One weekend in late January, each dorm competes against one another in several events spanning over three days, beginning on Friday afternoon. Having started over two decades ago as simply The College Bowl, a Trivial Pursuit style game, Winter Weekend has slowly evolved into roughly fifteen different activities and events. While the specific activities change from year to year, typical competitions include: The College Bowl, pep rally scavenger hunt, dorm skit/video, and a snow sculpture competition. During this weekend, dorm participants traditionally don clothing in their respective dorm colors, and judges distribute points not only to the first, second, and third place holders of events, but also to dorms that display spirit, participation, and respect throughout the weekend. In the following week, the scores are tallied up, and the victor is announced.
Occasionally, astonishing results will be produced from the effort put in by a dorm to win Winter Weekend.

• In the 2004 - 2005 school year, Case Hall constructed a fully functional hot tub out of ice for the snow sculpture competition. The ice blocks used to form the structure were molded from recycling bins, and insulation was provided by hay, towels, and tarps. A pump system siphoned water from the hot tub and circulated it through a heated radiator before returning it to the main tub at a temperature of 120°F.
• Case Hall's dorm video [1] for the 2008 - 2009 school year demonstrated an unprecedented level of attention to the event.

Case Hall had achieved first place every year since the start of the Winter Weekend tradition in the late 1980s, until the 2011 Weekend, in which Burton Hall took first place and became the first dorm to ever beat Case. Their victory came by just four points. The victory did not come without some controversy. For the first time in the weekend's history, all of the scoring information was not made public or announced to the student body and the scoring that was made public showed Case Hall ahead of Burton in points.
 
The Empire Cup is a huge attraction for Millbrook Students. During the last week of February, after the conclusion of the regular season, Milbrook School and Trinity-Pawling school host the Empire Cup hockey tournament. The tournament consists of 8 teams in two divisions, with Millbrook and Trinity-Pawling hosting their own divisions. The tournament is single elimination format, the winners of game one in each division play each other - and the losers play each other as well. The winner of the second game advances to the finals. The finals take place at either Millbrook or TP, based on a yearly rotation. The students of Millbrook take great pride in this last sporting event of the Winter term, as most of the school shows up for each of the Mustangs' games because there is nothing else to attend; Millbrook is miles away from any form of civilization. Students paint faces, wear jerseys of players and bang drums. Loud chants of "You can't do that!" when the opposition gets a penalty echo of the walls of the Bontecou rink. Teams that have been frequent to the tournament in its 10 year history have been: Hill School, Lawrenceville, The Albany Academy, NJ Avalanche, Wyoming Seminary, and Portledge School.