Bilal Hadfi, 20, named as one of the attackers who detonated a suicide bomb outside the Stade de France in Paris on November 13, attended the Anneessens-Funck college in Brussels until he dropped out in February to travel to Syria.
Paris attacker met in UK with suspected extremists: report
The two Belgian Dutch-language newspapers, De Morgen and Het Laatste Nieuws, cited documents they said showed staff were seriously concerned about Hadfi's extremist views, which were evident in the classroom.
The reports did not elaborate on the exact nature of the documents but said they showed the college director informed the Brussels education board in April that Hadfi, a French national, had traveled to Syria.
"Committee P" (le Comite Permanent de Controle des Services de Police), as the Belgian police oversight authority is known, is investigating why the information was not passed on to police, the newspapers said.
Neither the college, Committee P nor the Brussels education board were immediately available for comment.
Father of Paris attacker 'would have killed son' if he knew of plot
While there has been little hard evidence of intelligence and tip-offs falling between the cracks before the Paris attacks, Belgium has faced international accusations that underfunding and political in-fighting had left its security services the weakest link in Europe's counter-terrorism defenses.
It was not clear when Belgian security officials became aware that Hadfi has traveled to Syria.
But on his return to Europe he evaded the intelligence services. They bugged the apartment he had been registered at, but he failed to show up, so could not be traced.
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