"It was a crazy act by a youth who is unstable and fascinated by guns," Najat Vallaud-Belkacem said near the high school in the town of Grasse where the shooting occurred.
"The head teacher rushed towards (the student) to try to reason with him," Vallaud-Belkacem said, calling his response "heroic".
"We avoided the worst," she added.
The teacher was hospitalised with a gunshot wound and two pupils had buckshot injuries while five others were hurt in a stampede prompted by the attack.
The identity of the 17-year-old suspect has not been disclosed.
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