Jack first practiced law as a civil rights lawyer with the NAACP Legal Defense Fund and then moved to teaching at Columbia Law School where he focused on providing legal services to low-income persons and training students in the human dimensions of law practice. While at Columbia, he also directed a project funded by the NIMH and trained law teachers in humanistic approaches to law teaching, including the first trainings in mediation. Jack then became a co-founder of the CUNY School of Law, where for ten years he helped develop and guide innovative and experiential approach to training of lawyers in the public interest. During those years, he started his work with the Center and has since then devoted full time to developing and teaching the Understanding-based approach to resolving conflict and practicing mediation.
He is co-author, with his colleague Gary Friedman, of Challenging Conflict: Mediation Through Understanding, published by the American Bar Association in cooperation with the Harvard Program on Negotiation (co-winner of the 2008 CPR International Institute for Conflict Resolution Outstanding Book Award).