• Sammy Politziner


    Sammy graduated from the University of Michigan and moved to New York City, where he taught second grade in the South Bronx with Teach for America and founded a small academic summer camp for his students.  After a stint of world traveling, Sammy moved north for a master’s degree from the Harvard Graduate School of Education and then down south to teach at a KIPP school in North Carolina.  Sammy returned to New York for a job in investment banking at Kildare Capital, a boutique firm, where he spent five years providing sell-side M&A and capital formation advice.

    When not co-leading Arbor Rising, Sammy often dreams of starting a family band, running marathons in faraway lands and Michigan football winning the national championship (or at least reliving the glorious recent victories over Ohio State again and again).

  • Scott Thomas


    Scott earned an engineering degree from the University of Michigan, which he promptly misplaced and came to work as a middle school mathematics instructor through Teach for America in NYC’s Washington Heights neighborhood.  After another left turn to collect an MBA from NYU, Scott joined Lehman Brothers and later Neuberger Berman, where he helped manage investments in infrastructure and alternative energy companies.  Feeling the call to unite the social justice and business aspects of his career, he co-founded Arbor Brothers (now Arbor Rising) with Sammy in 2010 and continues to co-lead it today.

    Scott is grateful to serve on the board of Summer Search, a national youth development organization.  He has had the opportunity to guest lecture at Harvard, Columbia & NYU and is a member of the Leap Ambassadors Community.  When he’s not in the office he can be found chasing his Tasmanian-devil children and dog through the parks of Brooklyn.

  • Rebecca Cullen


    Prior to joining Arbor Rising in 2020, Rebecca served as the President at College Advising Corps, a national college access organization, where she oversaw a $45M budget and led 50+ staff members to increase opportunity annually for 200,000+ low-income, first-generation, underrepresented students. Before College Advising Corps, Rebecca fostered her passion for social justice at the Jack Kent Cooke Foundation where she spent more than a decade developing scholarship programs to advance the education of high-achieving, low-income students across the country. Earlier in her career, Rebecca managed an after-school learning center at Kaplan, worked in independent school admissions, coached refugees to find employment, and taught English in Russia.

    Rebecca earned her BA in history at Georgetown University. She enjoys travel, yoga, walking, tennis, and singing.

  • Rochelle Sinclair


    With a bachelor’s degree from New York University and an MBA from the University of Michigan, Rochelle began her career as a strategy consultant with PricewaterhouseCoopers (PwC) assisting clients through mergers, acquisitions, and growth through innovation. Fueled by her passion for equity and liberation, she transitioned to social impact work through a fellowship with The Broad Residency in Urban Education. Over the years, Rochelle has launched a statewide school improvement initiative at the New Jersey Department of Education and designed a teacher development program at Harlem Village Academies.  Most recently, Rochelle served as the Executive Director in New York for OneGoal, where she led her regional team towards increasing access, opportunity, and postsecondary completion rates for thousands of students across NYC.

    Rochelle joined Arbor Rising in 2023. She enjoys cooking in her free time and singing and cuddling with her kids at all times.

  • Courtney Tran

    Engagement Manager

    Courtney’s interest in social impact work began in California, where she served on the Oakland Public Library’s Youth Leadership Council, volunteered with the Berkeley Anti-Trafficking Coalition and supported research into social determinants of health in America. After graduating from UC Berkeley, Courtney moved to New York to complete a fellowship at Human Rights Watch, where she investigated attacks on medical facilities in conflict zones. She then completed an international development fellowship with the International Innovation Corps and the Self-Employed Women’s Association in India before returning to New York to earn a Master’s in International Affairs at Columbia University.

    Courtney joined Arbor Rising in 2020. In addition to her human rights and development background, she has nine years of private teaching and tutoring experience.


  • Melanie Jiménez

    Senior Associate

    After receiving a bachelor’s degree from UC Berkeley in 2016, Melanie spent a year as a research fellow at a Policy organization in Oakland, CA. In Oakland, she developed a strong interest in community impact and over the next 5 years, she applied this interest through a philanthropic lens at San Francisco Foundation (SFF). Through partnering with organizations and fellow funders, Melanie better understood what community impact could look like at a local level through relationship-building and strategic funding. During her years at SFF, she became the Program lead for the Foundation’s Program Related Investments and oversaw multiple grantmaking portfolios focused on anti-displacement efforts and community wealth-building through collective ownership over land, housing, and business. She then moved to the East Coast and pursued her Master’s in Social Policy from the University of Pennsylvania.

    Melanie joined Arbor Rising as a Senior Associate in 2022.

  • Caroline Ostrover

    Senior Associate

    Caroline graduated from Yale University in 2017 with a BA in American Studies. Her passion for youth development began in New Haven, where she worked as a volunteer tutor at New Haven Reads. After graduating, Caroline spent three years working as an art advisor at Sotheby’s and Murphy & Partners in New York City. She then earned a Master’s in Business Administration from Columbia University. During this time, she served as a member of the Nonprofit Board Leadership Program and the Harlem Tutorial Program. She gained further experience working to provide youth with meaningful opportunity as a Business Development intern with Juma Ventures.

    Caroline joined Arbor Rising as a Senior Associate in 2022. She is passionate about the outdoors, art, reading fiction, and college football.


Founders' Story

Sammy Politziner and Scott Thomas met while freshmen at the University of Michigan. Their friendship has been built on a shared thirst for adventure travel, avid fandom of Michigan sports, and, as it has turned out, a passion for social justice. After both serving as educators through Teach for America, they managed to navigate graduate school and careers in finance while preserving a tradition of annual pilgrimages back to Ann Arbor.

On one such trip, in 2008, they realized they both yearned to be a “part of the solution” to the challenges they saw in their adoptive home of New York City.  After two years of tackling pilot projects on nights and weekends, this instinct eventually evolved into Arbor Brothers – a nonprofit focused on empowering low-income families to secure a path out of poverty by providing crucial supports at critical moments to high-potential nonprofits. Arbor Brothers became Arbor Rising in 2022.

Board of Directors

This core group of supporters bears fiduciary responsibility for the organization and ultimately selects the constituents of each grant portfolio.

  • Ingrid Dyott

    Arbor Rising Board Chair | Neuberger Berman (retired)

  • Greg Geiling

    Managing Director, Co-COO at Bayview Asset Management, LLC

  • Ken Glassman

    CEO & Chief Investment Officer of RWN Management, LLC

  • Geoff Goldstein

    Managing Director at JLL Capital Markets

  • Erica Hamilton

    CEO & Founder at The Memo I Never Got (MING)

  • Scott Lebovitz

    Partner, Global Co-head of Infrastructure Investing & Head of Energy Investing at Goldman Sachs

  • Sammy Politziner

    Co-founder of Arbor Rising

  • Chris Rush

    Head of Research & Development (K-12 Education) at The Gates Foundation

  • Dana Sirota

    Pediatrician at Columbia University

  • Francisco Tezen

    President & CEO at A Better Chance

  • Scott Thomas

    Co-founder of Arbor Rising


Board of Advisors

From the beginning, the generously shared insights of these experienced advisors have played an instrumental role in Arbor Rising's development.

  • Jamar Adams

    Founder and Managing Principal at Essence Development, All-Big Ten Safety at Michigan

  • Cathy Bacich

    Arbor Rising Board Member (2012-2019)

  • Nick Ehrmann

    Managing Director of Impact at Arena Holdings

  • Michael Ellis

    Managing Director & COO at Inherent Group, Founding Board Member of Arbor Rising

  • Peter Frey

    Private Investor; Partner at TRG Management (retired)

  • Matt Klein

    Chief Program & Impact Officer at Robin Hood

  • Rich Leimsider

    Social sector leader

  • Peter Marrs

    Managing Director at EY

  • Nitzan Pelman

    CEO and Founder of Climb Hire

  • Jessica Sager

    Co-Founder and Chief Executive Officer of All Our Kin

  • David Sambur

    Co-Lead Partner, Private Equity at Apollo Global Management

  • Emily Keenan

    Founding Arbor Rising Board Member (2010-2023)



We are extraordinarily grateful to the people who power our work: our donors.

This generous group of families and foundations has refused to accept that life circumstances should dictate access to opportunity. Since 2009 their investments in Arbor Rising have helped build and sustain organizations working every day to transform the lives of young people in our community.

Contribute to the Solution

Arbor Rising finds, funds, and deeply supports the most promising second-stage nonprofits in the tri-state area.