New York-born Charles Dormer will take over as headteacher at Immanuel College after the retirement of Philip Skelker at the end of the academic year.
Mr Dormer, 44, holds dual American and British citizenship. He studied English at Magdalene College, Cambridge, and is currently head at the King's School, Grantham. He has 23 years of educational experience.
He said it would be "a privilege to have the opportunity to build on the legacy of Philip Skelker, who inspired pupils and staff to sustain the school's unique set of values.
"I look forward to leading Immanuel College and to furthering the academic excellence, expert pastoral care and inspiring Jewish education it provides."
Richard Segal, co-chair of governors of the 500-pupil Bushey school, said the new head "has all the requisite qualities, experience and energy to strengthen this excellent school".