Lappas graduated from Bronx High School of Science in 1972, where he was sixth man on its 1971 city championship team and a starter as a prep senior.

He went on to the City College of New York, where he was a three-year letterwinner in basketball and served as the team's captain in his junior season.

After one season, he assumed his first head coaching job with Harry S. Truman High School (in The Bronx), staying there through 1984.

[3] Harry S. Truman High School won a New York State Class A championship under Lappas in the 1983–84 season, during which it was 27–3.

[1] In 2001, he resigned as head coach after Villanova declined to sign him for a long-term contract due to multiple years of poor recruiting, and a subsequent lack of success in the postseason.