That's according to Joanna Shuter, his former head teacher at Quintin Kynaston Community Academy in northwest London.
Now 26, Emwazi has gained international notoriety after being identified as the ISIS militant nicknamed "Jihadi John" who's appeared in beheading videos of Western hostages.
But in his school days, it was a different matter. When he joined Quintin Kynaston at 14 or 15, he was little trouble himself but was the focus of some bullying.
"He was bullied a little, but because he was quiet and he was reserved ... generally he was fine," Shuter said.
"There were no massive behavior problems with him, and by the time he got into ... (his last years) he had settled, he was working hard, he achieved great grades for him, and he went to the university of his choice."
He just didn't stand out as troubled, she said.
"If there had been any concerns about Mohammed, they would have been picked up, and we would have intervened and tried to support him in any way that we could have done."
School had ethos of tolerance
Born in Kuwait, but brought up in London from the age of 6, Emwazi was one of the school's many students from an immigrant background.
The school's intake is 70% Muslim, said Shuter, with many students coming from large housing estates in what is a multicultural area of London.
But its ethos was one of tolerance and integration, with all students encouraged to feel part of the school community. Staff made great efforts to get to know the 1,400 students in the school so that nobody would feel excluded or left behind, Shuter said.
They also reached out to the sometimes insular, conservative Muslim communities that many of their students came from, she said, to try to help students who could feel torn between different cultures.
Nonetheless, Emwazi was somehow drawn in by radical influences, most likely outside of school or through social media.
And he was not alone. At least two other students who attended Quintin Kynaston also allegedly later turned to Islamist extremism.
One, Mohammed Sakr, only overlapped at the school by a few months with Shuter. He was reportedly killed in a U.S. drone strike in Somalia
"He was very outgoing, jolly, sporty kind of person and fun," Shuter said.
'My blood just ran cold'
Shuter sees social media as the greatest danger facing young people and their families today.
"I think social media is terrifying because it does have the power to influence young people in a way that as adults we have no power to control," she said.
She still finds it hard to believe that Emwazi could be the apparent killer with the London accent recorded on ISIS videos.
"My blood just ran cold," she said of when she first heard the news.
"When I hear the name, I just find it incredible to marry what I've clearly seen on the TV with the person that I knew. It literally makes the hairs on the back of my neck stand up. I can't believe what has happened to him and the influences that clearly have completely changed him.
"I think it's horrific, the idea that a young man like that could become somebody that people say is the poster boy for (ISIS). I just think it's shocking."
Audio recording released
The London-accented voice is all too familiar to anyone who's watched the videos released by ISIS of the killing of Western hostages.
CAGE, a London-based advocacy group that worked with Emwazi, has released audio of a phone conversation from 2009 in which he talks about members of the UK security services questioning him.
They asked about his attitude toward the July 7, 2005, terror attacks in London and the 9/11 attacks on the United States, he says.
"We're going to keep a close eye on you, Mohammed," he alleges they told him.
CAGE has painted a picture of a young man driven to extremism by unwarranted harassment by security services.
It says emails he sent the group
paint a picture of a desperate man hounded by authorities who saw his plans for a new life crumble as he tried unsuccessfully to get help.
But some analysts say the emails are only part of the story
, arguing that investigators targeted Emwazi because they already saw he had links with terrorist groups.