During the 2007–08 school year, Millburn School was recognized with the Blue Ribbon School Award of Excellence by the United States Department of Education, the highest award an American school can receive.
In its 2015 report on "America's Top High Schools", Newsweek ranked Millburn the #1 open-admission and #4 non-magnet school in the nation. It placed 13th overall in the U.S. and 8th in the state among all participating public high schools (including selective admission and magnet schools). All schools ranked above Millburn are magnet programs that use selective enrollment.
In its 2013 report on "America's Best High Schools", The Daily Beast ranked the school 69th in the nation among participating public high schools and 6th overall (and the highest-ranked non-magnet school) among schools in New Jersey. The school was ranked 83rd in the nation and fourth in New Jersey on the list of "America's Best High Schools 2012" prepared by The Daily Beast / Newsweek, with rankings based 25% each on graduation rate, matriculation rate for college and number of Advanced Placement / International Baccalaureate courses taken per student, with 10% based on average scores on the SAT / ACT, 10% on AP/IB scores and an additional 5% based on the number of AP/IB courses available to students; It was the highest-ranked open enrollment (non-selective / non-magnet) school in the state.
In the 2011 "Ranking America's High Schools" issue by The Washington Post, the school was ranked 4th in New Jersey and 236th nationwide. The school was ranked 170th in Newsweek's 2009 ranking of the top 1,500 high schools in the United States and was the second-ranked school in New Jersey, with 3.165 AP tests taken in 2008 per graduating senior and 56% of all graduating seniors passing at least one AP exam, after being ranked 151st in 2008. In Newsweek's 2007 ranking of the country's top high schools, Millburn High School was listed in 165th place, the third-highest ranked school in New Jersey. The school was 181st, sixth-highest in New Jersey, on Newsweek's May 8, 2006, list of 1,200 U.S. high schools. Millburn High School was ranked as Number 148 in Newsweek's 2005 rankings.
The school was the 5th-ranked public high school in New Jersey out of 339 schools statewide in New Jersey Monthly magazine's September 2014 cover story on the state's "Top Public High Schools", using a new ranking methodology. The school had been ranked 8th in the state of 328 schools in 2012, after being ranked 1st in 2010 out of 322 schools listed. The school had also ranked highest in the state in the magazine's 2008 report. The school was ranked 3rd in the magazine's 2006 rankings out of 316 schools included across the state.