In Judaism, the Bar-Mitzvah ceremony marks the transition from childhood to adulthood. According to Jewish law, when Jewish boys reach the age of thirteen, and girls the age of twelve, they become responsible for their actions, and join the congregation of adults.
On the day of the ceremony the boys (and nowadays many girls as well) read a bible portion in synagogue in front of the entire congregation. The boys start wearing Tefillin for the first time. The Bar Mitzvah is also a time of family celebration, and gifts.
Only a few children were able to celebrate their Bar-Mitzvah during the Holocaust. For those who did, it became a special, significant experience. The risk was usually high, and the conditions in the ghetto made it very difficult to celebrate the ceremony.