"Able children who sail through school can collapse when they meet something they can't do or meet a setback," Mr McLean, an educational psychologist with Glasgow City Council, said.
Best known for his book The Motivated School and his work on Glasgow's "social emotional learning framework", which is being rolled out across Scotland, Mr McLean last week addressed the Scottish Network for Able Pupils (Snap) on how schools could best meet the needs of the most gifted students.
"The crucial difference between children is how they feel about themselves -that is what drives all your children," he told a seminar. What children needed were teachers who had the flexibility of an orchestra conductor, who could take an overview of the class and each pupil in it, and bring out the best in each one.
Mr McLean stressed the importance of children having an "affiliation" or sense of connection with their school, and warned that those who felt alienated or rejected lost their self-focus.
Margaret Sutherland, a researcher at Glasgow University's education faculty and a member of the Snap project team, said that many able pupils lacked affiliation with their peers. Many of their parents told her they just wished their child was "normal".
Able pupils coped well as long as they had good social skills. If they lacked these, they were seen as "nerds" or "geeks". They were often the first to come up with answers but did not always make good team leaders because they were impatient of others' inability; they could be difficult to teach because they sometimes knew they knew more than the teacher, Mrs Sutherland said.
Mr McLean's description of the "hiding" child - who prefers to be invisible in the classroom - also struck chords with Mrs Sutherland. "What happens to the able pupils is the teacher lets them get on with it because they are doing well enough," she said.
Mrs Sutherland advocated allowing very able children to learn alongside older students. When interviewing able children about how the Additional Support for Learning Act might meet their needs, she found they complained about having to follow the class curriculum and then doing more advanced work after school.
In effect, they were asking: "Why do I have to go to after-school to get what I need?".
She said: "The message is starting to get out there - if we are going to be operating a truly inclusive system we can't exclude this group."