"This act of barbarity and murder will be met with a Jewish response," said Rabbi Aryeh Goldberg, deputy director of the Brussels-based Rabbinical Centre of Europe (RCE).
"We will bury the dead, look after the injured, and we will demand justice is pursued through the appropriate channels," he said.
The victims were killed on Monday when a gunman opened fire outside the Ozar Hatorah school in Toulouse, southwest France.
"This attack is an attack on the whole Jewish community; we feel the pain of the families who have lost loved ones and as a community we will show our reaction," Goldberg said in a statement.
"If there are people who want to scare the Jewish community into submission, our response will be to show them that we will not be bowed, the opposite is true. We will build more schools, synagogues and other Jewish institutions."
The European Union's home affairs commissioner, Cecilia Malmstroem, also reacted to the shooting, calling it "horrible" on her Twitter account.