A ground-breaking ceremony was held on Tuesday to mark the start of building work at Immanuel College in Bushey.
An eight-classroom block costing nearly £1 million is planned for completion in time for the next academic year. The classrooms will be multi-functional, providing large or more intimate teaching areas and an examination hall.
"We are investing for the future of Immanuel College," said governors' chair Dr Sara Levene. "This new block will add state-of-the-art facilities to the campus".
Addressing pupils and staff at an assembly following the ceremony, UJIA chairman Mick Davis said: "Jewish schools do not create separateness, but rather help nurture a value of service to society and one's fellow man."
Immanuel head Philip Skelker spoke of "a great increase in the level of student achievement in recent years. The new building is central to the next phase of our development."