In September 1941 Hertog Hein Izak van Gelder was enrolled in Grade 1 of the grammar school in the Hague. In October 1941 Hertog Hein Izak van Gelder had to transfer to Grade 2b of the Joods Lyceum.
Data on Jewish students at schools in The Hague.The records of the Joods Lyceum in The Hague contain Lists of students at schools in The Hague, including a list of students at the Joods Lyceum. These records are kept at the municipal archive in The Hague.