At the heart of every good school lies a group of teachers who hold sacred their mission to create the very best opportunities for all of the children in their care. In a great school, every child will have their emotional, physical, intellectual, spiritual, aesthetic and moral needs stimulated, and they will all become the best that they can be. These are the high aspirations of those who dedicate their lives to schools and the noble art of teaching.

These are the lofty objectives of us all, and while they help to inspire our profession, they are also a curse. Good schools need good teachers and the triumph of school management is the delivery of these great teachers to the chalkface. Not only do governors and headteachers have to create a strong group of teachers, they have to maintain it so that natural wastage and career progression do not weaken the team. All school teams are continually evolving and the real challenge is to maintain that team year after year.

How can this be achieved in the financially challenged times in which we find ourselves? Not only is real-terms funding reducing, but we are increasingly being asked to do more and more with the scant resource that is a school’s budget.

The answer to our staffing issues lies emphatically with “growing our own”. The development of school-centred initial teacher training (SCITT) has opened the floodgates for schools to train their own.

This can be done by doing SCITT or by joining in a school partnership. Either way, the opportunity is there for those with the energy to pursue the goal of a continual supply of great teachers.

There are many examples of this working well and large groups of schools are collaborating to create truly lasting partnerships that will maximise the opportunities for young people. While this may sound like an easy solution for some, others would maintain that it is not a solution for them, as it would drain resources and divert much-needed energy and time from other essential tasks.

All of which leads us to a great - and overdue - debate that needs to be had about what exactly schools should be doing with their time. When does the role of teacher trainer conflict with the teacher’s role with pupils? How can a school concentrate on pupil outcomes when they are training teachers?

Let us for a moment consider the cost of state education and, for the sake of simplicity, assume that each school receives about £4,000 for each primary child. Simple maths will lead us to the figure of £11 per child per day (£16 in secondary). These are clearly notional figures and variations will occur. The school day (say 9am to 4pm) of 7 hours equals £1.57 per hour per child. By any measure, this is remarkable value for money. By the way, don’t be led to believe that we should only consider term-time costs - the school functions throughout the year (staff are paid annually).

The cost that broke the camel’s back

So the big question is, what can we as a nation expect to be included in this funding allowance? Can we expect everything to be funded centrally (clubs, trips, visits, sport)? This discussion is both challenging and concerning because we have spent many years including and extending the range of school activities and generally meeting the cost from central funding. There clearly comes a point when this stops working well. Perhaps increased staff workload has been the ultimate cost that has broken the camel’s back.

What if we were to think differently and challenge the concept that everything in school is free at the point of delivery? I have visited many schools and it is clear to me that some give much better value for money than others. Is now the time to make explicit what is free and what is not?

If we look at a close public service relative, the NHS, it is clear what is “free” and what has to be paid for. For instance, few would expect to get spectacles free of charge unless there was a clear medical condition and certain drugs are not available, as the cost to the public purse is not seen as acceptable. This analogy is not perfect, but what I am arguing is that perhaps now is the time to generate a real national discussion about what is in and what is out of free state education.

We should not be shy about this debate because, of course, it has been running for many years. As a young teacher, I remember the introduction of fees for instrumental music tuition (yes, it was once free). School trips are clearly a charged activity, as well as after-school care and breakfast clubs. The problem with the current arrangement is that it has all developed in a rather random and haphazard way that has left schools making their own arrangements; this has created uncertainty for parents and, I would suggest, an unbearable burden on some school budgets.

What if we were to be explicit in this work? Indeed, rather than start from the promise of reducing entitlement, we could raise the bar of expectation for parents and create a real bargaining position for the government when asking for increased funding for education.

By “coming clean” on what can be reasonably expected, we make way for perhaps the most challenging aspect of this notion. If the state has a “core offer”, supported by “core funding”, who pays for the “extras”? Perhaps this is where the real focus of “pupil premium” comes into play.

Let’s not pretend that there is no cost in the extras. It is paid for by extra time (often given freely by teachers) and by parents supporting schools directly, as well as by entrepreneurial schools using their schools to generate extra income. The problem is, it does not create a truly universal offer for every child.

Which brings us back to where we started. Is there really a shortage of teachers that is beyond our control? Or could a new approach to school finance free up schools to think imaginatively about how they fund teacher training on their sites? Or must we remain like the “poor man at the gate”?

Let us be bold and tell it as it is, and I’m sure the nation will respond by serving its young in the best way possible. We must think that which was once considered impossible. In our “self-improving school system”, the future belongs to the brave.

Sir Andrew Carter is CEO of South Farnham School Educational Trust and was chair of the government-commissioned Carter Review of initial teacher training