One week after winning its second Ivy League title in a row the Horace Mann School Girls Varsity Basketball team captured the New York State Association of Independent Schools championship. The top seed going into the game against Masters School on Monday night, February 24, 2020, the Lions led from the start, winning with a score of 55-33. The win marked the first NYSAIS for HM's Girls Basketball team since 2000.

The Horace Mann School Girls Lions Basketball team claimed the 2020 Ivy League title following a decisive win over Riverdale Country Day School in the annual Buzzell Games on Friday, February 14, 2020. The win brought the team its second consecutive Ivy League Championship, with a 12-0 record in the league. The team's 2019 championship brought HM its first Girls Basketball title in 21 years.The Girls Varsity Lions Basketball team has been ranked number one in New York State in its Class B category by the New York State Sportswriters Association (NYSSWA) since Feb. 11, 2019, topping a list of 25 teams from around N.Y. State in their category (AIS/Association of Independent Schools). The team faces its final challenge—the New York State Association of Independent Schools (NYSAIS) championship game against Masters School on Feb. 24, 2020, at 7 p.m. at Fieldston High School.

Horace Mann School senior Brian Wu '20 was named one of 40 top scholars in the 79^th Regeneron Science Talent Search, the Society for Science and the Public announced on January 22, 2020. Wu was selected from among the 300 top science students nationwide announced by Regeneron on January 8, 2020. This list was narrowed down from an original 1,993 highly qualified entrants from 659 high schools across 49 states, Washington D.C., Puerto Rico, Guam and eight countries. Each submitted an original research project for the nation's oldest and most prestigious science and math competition for high school seniors.

The holiday season is a time of tradition. A favorite tradition at Horace Mann School is the annual holiday dinner students host on behalf of children and parents served by Sanctuary for Families, an organization assisting victims of domestic violence and their children. The evening of December 11, 2019, marked this get-together's 27^th year. The dinner brought some 150 mothers and their children, babies through teens, to HM's Cohen Dining Commons for a party featuring craft-making, face-painting, games, and a delicious meal of turkey and all the trimmings, with holiday-themed cake for dessert. The evening began with each child invited to choose a book to take home, upon entering the festively decorated space. The children all left with a specially-packed present, while each mom received an Amazon gift card. In between, the children and parents practiced a line dance taught by members of HM's Upper Division Dance Company, and listened to holiday favorites performed by the UD's Jazz Combo.

Three Horace Mann School alumni were among the honorees in the "Forbes 30 Under 30 Class of 2020," announced on December 3, 2019. The Forbes list presents a selection of 30 honorees in 20 different categories, for a total of "600 young entrepreneurs, risk-takers and game changers who are redefining what it means to innovate and lead by example," according to Forbes.com. This year's honorees were selected from among 15,000 nominees, vetted by judges who included experts in each field, along with "the world's top investors and entrepreneurs."

For the Horace Mann School community, and its art students in particular, the first months of the academic year were enhanced by a special exhibit in the school's Art Gallery. The exhibit, titled "Ways of Seeing" presented deeply evocative paintings by artists from the legendary Blue Mountain Gallery, one of New York's oldest artist-run galleries, together with works by HM student artists.