Mohammed Emwazi, who has been seen in beheading videos of Western hostages, attended Quintin Kynaston school in QueensPark, north westLondon, a decade ago.
His former teacher said Emwazi needed help controlling his emotions but he was regarded as a "success story" after the therapy, she added.
Emwazi was unveiled as a Kuwaiti-born British man in his mid-20s leading to criticism of UK security services for being aware of him but not preventing him from joining Islamic State.
"We'd find that he'd get very angry and worked up and it would take him a long time to
"It seemed to work. He had a lot of respect for all of the work that had been done for him at our school," she said.
A statement from Quintin Kynaston school said it was "shocked and sickened" that its former pupil may be involved with Islamic State.
"All members of staff at QK work very hard to support the education and well-being of our students and protect them from harm," it said.
"In this respect, QK has been extremely proactive in working with the government's prevent strategy for a period of time and will continue to be so for the foreseeable future,' it added.
British Prime Minister David Cameron has defended the UK's security services, praising the work of "these extraordinary men and women" and vowed to put such extremists "out of action".