Hackers, hair and hands: former FBI director James Comey’s revelations about Donald Trump’s White House were entertaining and alarming in equal measure. But Comey reserved arguably his most savage criticism for the process of presidential leadership itself, and the “silent circle of assent” that allowed allegiance and loyalty to override rational, critical approaches to decision-making.

Situations such as this are less rare than you might imagine. From MPs’ expenses to executive pay, from systemic failures in health and education policy to muddle-headed vanity projects (think “garden bridge across the Thames” ), many a flawed initiative has, at its origin, a phenomenon that psychologists refer to as “groupthink”.

Groupthink occurs at all social levels and across all sectors and industries. It happens when the entirely normal human pursuit of social harmony has the effect of stifling alternative viewpoints and suppressing dissent. It takes place when leadership teams are formed of people with overly similar backgrounds, and when members isolate themselves from outside influences and uncomfortable or challenging opinions. Decisions are reached with an illusion of unanimity, arrived at in echo chambers characterised by self-censorship and an absence of contradictory views.

There are historical precedents for leaders acknowledging the perils of Comey’s “silent circle of assent”.

In ancient Rome, for example, the Auriga was a slave with the task of holding a laurel crown over the head of the Dux (leader) during a triumphal parade, while whispering the words “Memento homo” in his ear, meaning “Remember, you are only human”.

In modern times, some of the most creative and innovative commercial leaders have succeeded by embracing dissonant voices. Eric Schmidt, until recently executive chairman of Google, has written about how we should “fight for divas” - those exceptional employees who “refuse to be normal”. They may, he says, come in passionate, discordant or maverick form; they may sometimes be high maintenance, but their disruptive thinking can be of immense value.

Schools are more prone to groupthink than many institutions, since they are often characterised by hierarchical rigidity - horizontally as well as vertically. The tumult of an average school day and the presence of small, often highly cohesive departmental units, can mean that the informal, undefended sharing of ideas between ordered tiers is neither meaningfully nor regularly pursued. So how can schools avoid the silent circle of assent?

Encourage scepticism

Recognise that leadership teams are instinctively self-preserving. Cohesiveness is important, as is teamwork, but so, too, is encouraging healthy scepticism and creative conflict. Self-appointed “thought guardians” can actively prevent bad news or difficult views from reaching the leader, but suppressing dissent is risky and can lead to teams becoming overly, even dangerously, optimistic about their own capabilities and aptitudes.

Consider the options

Ruthlessly insist upon alternatives. Many a disappointing reform or failure is the result of an incomplete survey of the options at the outset. Improvement requires approaches to be challenged - a sacred cow or two to be slaughtered. Is the proposed choice really the best? What is the alternative to that alternative? And the alternative to that? Yes, it is time-consuming. But making substantial changes to the professional practice of a workforce warrants a scrupulously careful survey of all avenues.

Embrace devil’s advocates

Mavericks and alternative thinkers are our friends in the process of change, so consider the make-up of the leadership team. Is there room for a disbeliever - an occasionally irritating but always invaluable person who says “Yes, but”? The best criticism of a good idea leads not to rejection but to revision, improvement and eventual acceptance.

Follow the ‘two pizza rule’

Are meetings so large that they become inhibiting or intimidating, discouraging people from speaking their mind, especially if their views go against the tide?

Jeff Bezos, founder of Amazon, follows the “two pizza rule”: to maximise productivity and creativity, and to avoid a table surrounded by silently nodding heads, never hold meetings where more than two pizzas would be needed to feed everyone there.

Learn from others’ mistakes

The desire to innovate and to lead are powerful and positive forces. But consider whether the institution will benefit more from waiting, watching, drawing on the experiences of others and taking time to canvass opinions from outside the team.

Decisiveness can be an over-prized quality if a fast decision is a flawed one.

Use evidence wisely

Data produced by singular, well-meaning but often agenda-driven colleagues can provide false comfort.

Leadership expert Jack Zenger, writing in Harvard Business Review in 2015, asserts that “good leaders make decisions carefully after collecting data from multiple sources and seeking opinions from those whom they know will have differing views”. So challenge, triangulate, pilot, hone.

Avoid isolation

Meet regularly and routinely with staff outside the leadership team. Do not wait for an emergency, a staffing crisis or the procedural constraints of an appraisal meeting to sit down with heads of core subjects, middle leaders and others.

Consider staff panels for key appointments. Avoid bogus consultations when too much time has already been invested in a project to permit deviations from it.

Without the tolerance or the inspiration of divas and disrupters, and without the encouragement of creative dissent, leadership can fester and fail. Unrealistic projects and impractical policies can be nodded through by overly affirming team players, keener to preserve cohesion and unity than to benefit from engagement with constructively critical or sceptical views.

Nick Gallop is head of Stamford School, an independent day and boarding school in Lincolnshire