The teenager, who told police he was acting in the name of the Islamic State group, stabbed the 35-year-old teacher in the shoulder and hand in the attack, which took place in broad daylight on Monday.
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The teacher's lawyer, Fabrice Labi, said his client had told him, "I had the feeling he wanted to decapitate me."
Marseille prosecutor Brice Robin said the weapon was blunt, which helped limit the damage. The teacher was released from hospital on Monday night.
"I told him to stop hitting me but he kept going and I didn't think I would get out alive,", the teacher told La Provence newspaper, adding he had seen "hatred... in the eyes of the attacker."
The teacher was wearing a skull cap and used his Torah as a shield to fend off the assailant.
It was the third attack on Jewish persons in recent months in the southern French port city, which has the second largest population of Jews in France after the capital Paris.
Three Jews were assaulted in October, one with a knife near a synagogue by a drunken assailant.
In November, another Jewish teacher was stabbed by people shouting anti-Semitic obscenities and support for the Islamic State group.
France's Jewish community has grown used to living under the surveillance of armed soldiers around synagogues and schools since being targeted in a militant attack in Paris last January.
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This weekend, the country marked a year since the attacks which left 17 people dead, including four people gunned down in a Jewish supermarket.
According to French government statistics, anti-Semitic acts have soared in recent years, with the number reported between January and May 2015 increasing 84 percent compared with the same period in 2014.
The growing insecurity has seen an increase in emigration to Israel, with record departures in 2015 of 7,900 people.
"Honestly, I don't know how I will get over this terrible attack," said the teacher, adding he would have to think about no longer wearing his skull cap in public.
The prosecutor Robin said the teenager, who will turn 16 in the coming days, "has the profile of someone who was radicalised on the Internet".
"He claimed to have been acting for Daesh," he added, using the Arabic acronym for the Islamic State group.
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"You get the sense that he does not have a full grasp of the fundamentals of Islam," he added.
The boy even admitted to investigators that he planned to arm himself and kill police as soon as he is released.
The prosecutor said the attacker was a "good student" whose family had been unaware of his radicalisation.
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