There is an exodus happening in education: teachers between the ages of 50 and 60 are leaving the profession in droves.

The proportion of teachers in this age bracket dropped from 21.7 per cent in 2010 to 15.6 per cent in 2016. Meanwhile, the proportions of teachers in all other age categories rose during the same period, and under-30s now make up 24.9 per cent of the teacher workforce.

What could be causing all these experienced colleagues to quit - besides the excessive workload, scrutiny and stress? The obvious answer may seem to be retirement. Yet, a closer look at the numbers reveals that this solution doesn’t quite add up. During the 2015-16 financial year, the number of teachers taking retirement was actually lower than in previous years.

So if teachers are not retiring early, why are they really leaving?

Let’s follow some of the clues. A 2010 survey conducted by the NASUWT teaching union found that one in three older teachers believed that they had been made to feel “less capable” than younger colleagues, and one in five felt that their “professional capabilities had been marginalised or undermined due to their age”. Then, in 2015, the NUT teaching union (now part of the NEU) shared anecdotal evidence that over-50s were being placed on capability procedures by “new broom” headteachers who “don’t value their experience”.

More recently, in April 2018, delegates at the annual NASUWT conference heard Wendy Exton, a member of the union’s national executive, speak about the “endemic discrimination” taking place in some schools, where older members of staff were accused of “poor practice” and lacking “classroom leadership”, despite being previously “graded by Ofsted as ‘outstanding’ ”.

Could it be that the problem is a simple matter of ageism?

I put the question directly to teachers in a Twitter survey, asking to what extent they agreed that staff over 50 were singled out by leadership teams and put under unwarranted pressure because of the presumption of incompetence. The choices I offered were “often”, “sometimes”, “rarely” and “never”. Of the 603 teachers who responded, 16 per cent said “often” and 34 per cent said “sometimes”. While my sample was small and included teachers of all ages, when taken in conjunction with the evidence from the unions, this feedback does suggest that classroom teachers over the age of 50 are being driven out of the profession.

‘Who needs fuddy-duddies?’

Personally, I have seen how older staff are treated with suspicion by schools: drop-ins last longer; GCSE groups are not on their timetables; and if they dare to openly say what everyone else is thinking and disagree with the senior leadership team? A “support” plan awaits them. Those “fuddy-duddies” are viewed as a drain on the system: with their outdated approaches and morale-sapping negativity, who needs them anyway?

While such prejudices are rarely expressed in public, they may be implied, and not only by the school leadership team. One cannot help but read between the lines when politicians make statements like Michael Gove did in 2013, when he said: “I am fortunate as education secretary because we have the best generation of teachers ever in our classrooms, including the very best generation ever of young teachers - those who have entered our classrooms over the last few years” (bit.ly/Gove_Speech). The message seems to be that younger is better. And, by implication, that if you’ve been teaching since the 1990s, you may as well clear your desk and be gone by the end of the day.

But why would schools - or politicians - be prejudiced against older teachers in the first place? Especially at a time of well-publicised “recruitment crisis”, one might assume that the wisdom and experience of older staff would be a valuable resource to support school improvement and to facilitate the mentoring of younger colleagues.

However, the problem is that all this experience comes at a price - quite literally. The longer a teacher teaches, the more money they earn. Those who entered the profession prior to the introduction of performance-related pay are likely to be costing the school significantly more than younger - and potentially “higher-achieving” - members of staff. And with school budgets being squeezed, it is perhaps no surprise that some senior leaders might begin to target the more expensive members of staff in response.

But there’s another problem, too. Younger teachers are often seen by hiring managers as easily “mouldable” and more energetic. They are also seemingly less likely to openly object to being asked to attend additional CPD sessions, run out-of-hours revision lessons or change their practice to accommodate the senior leadership team’s latest initiative.

Although budgets are tight, I am convinced that the targeting of older staff is less about austerity and more to do with the desire for humbly obedient teachers. In addition to this, some schools seem to be of the opinion that younger teachers are better able to relate to pupils - wrongly assuming that older teachers can’t do this. Hiring young blood and driving more experienced staff out then becomes a matter of the school supposedly doing “what’s best for the kids”. Age discrimination is quick to follow.

Whatever the justification, schools must stop the practice of pushing older class teachers out of schools. The message this sends to younger teachers is: “Get promoted, or else.” By disregarding older teachers who remain in the classroom, you cheapen the task of working directly with children - which is why many young teachers enter the profession in the first place. Schools need to set an example that continuing as a class teacher is perfectly acceptable.

What’s more, it is the height of hypocrisy to insist on teachers treating pupils as individuals - always condemning a one-size-fits-all approach - while at the same time ensuring that the majority of teachers fall within a particular age bracket. Let’s not deny our pupils the cognitive and social benefits they will likely receive from interacting with various adult personalities of all ages.

One of my favourite and most memorable teachers - Dr John Sleigh - was over 50 when he taught me chemistry. Nobody would ever have said that he couldn’t relate to young people or that his teaching methods were ineffective. Even back in the 1990s, he would have been more “expensive”, but the fact that I am mentioning him now, after so long, is more than sufficient justification for his salary.

There are many older teachers who will have an impact on young people similar to the impact Dr Sleigh had on me. Let’s keep them - for as long as we can.

Omar Akbar is a teacher and author of The (Un)official Teacher’s Manual: what they don’t teach you in training