After completing the 8th grade, his parents enrolled him in a yeshiva, but after three months, he was withdrawn. For high school, Vanunu attended Yeshivat Ohel Shlomo high school, a Bnei Akiva-run school, where he was an excellent student, earning honors. According to Vanunu, whilst in secondary school, he had a personal crisis which led to him deciding not to observe religious Judaism. In an interview, he said that "already at this stage, I decided to cut myself off from the Jewish religion, but I didn't want to have a confrontation with my parents because I wanted to complete my studies".