It's a good argument, and it's worth making it as strongly as she does.
When our mission creeps to far, the results are often rather disappointing. For example, I think Ofsted have shown pretty clearly that the schools with the best pastoral and curriculum support around healthy living seem to have no discernible impact on reducing obesity.
Similarly, research from the UCL Institute of Education is suggesting that one of the most powerful ways to support young children's social and emotional development is to concentrate on the core role of helping them to become better communicators, with a richer vocabulary. Focusing on the core job we have to educate children may have more impact than "mission creep" into other areas.
Causing more harm than good?
In my experience, specialist mental health interventions are needed for children in crisis. But some schools run nurturing and mentoring programmes which are staffed by well-meaning but poorly-qualified staff who don't have the supervision or support they need.
Whether these interventions cause more harm than good is a point worth considering.
Is it always a good idea to encourage children to talk about troubling and distressing things to a member of staff who hasn't been adequately trained? What is like for a child to return to the corridor, playground or classroom afterwards? Schools are not containing, therapeutic environments. Their therapeutic value rests, surely, in their capacity to help children achieve the pleasures of growth and development, and to socialise with other children, in an orderly environment with sensible and clear boundaries.
The early years are important - and different
This discussion about whether teachers should be involved in activities like toilet training does not apply in full to the early years. For example, in the nursery school where I'm headteacher we have many two-year olds on roll and of course many of them are not yet toilet trained. It's a task we share with parents.
It's also perfectly ordinary for a child just turned 3 and in a school nursery class to need help with toileting. The child may not yet have developed enough to have complete continence. Or they might be fine at home, but find things much harder in a large group setting, where the distance to the toilets is greater.
Finally, let's not forget that there was once a national programme to support parents in the early years: the Sure Start Children's Centre programme. The destruction of this programme in recent years ought to be a national disgrace.
Children who are being excluded from early years provision
This leads me onto a development which I find very concerning.
Some schools and settings are excluding children who most need nursery provision. The result of their actions is that the children miss out on their nursery education. When they arrive to start compulsory education in reception, they have needs which it's very difficult for a reception teacher to meet - as Amanda Spielman is arguing.
How does this happen?
Some schools put parents off, without actually saying their children aren't welcome.
For example, a parent recently told me of her visit to an early years open day at a local school. The executive headteacher spoke to all the parents and said that the school has "high standards". There is an expectation that children will achieve highly from day one in the early years and they are unashamed about "pushing" the children. All reception children are "expected" to enrol in an after-school club, so one day a week their school day will end at 5pm. Finally, the executive headteacher advised any parent who had misgivings to conclude that "this school might not be the right one for you."
I don't know how widespread these practices are.
The outcome of the open day was that the parents who knew their children would not be able to conform to those expectations went elsewhere. Many of those children will be younger, or less developed. Or they may have parents who have found setting behavioural boundaries or implementing routines difficult.
They are children who need nursery.
In our comprehensive system of primary education, their families should be able to access it.
In the case of the parent who spoke to me, her reason for turning away was simpler: she didn't want that type of early education for her son.
Here's another way it happens.
A nursery class in a primary school has a settling in policy which says what children must be able to do, before they can stay for all their sessions.
They must be able to stay awake and energetic throughout the nursery session. They must behave appropriately and non-aggressively for the majority of the time. They must attempt to manage their own personal hygiene needs.
On this basis, pretty much all of the most vulnerable children in the nursery schools I know would be prevented from accessing their full place.
No children from families with poor bedtime routines.
No children who need the extra help we can give them, in collaboration with their parents, to manage socialising with others.
No children needing extra help with toilet training.
They'd all be at home for the nursery year.
Then they would arrive in reception, and their needs would not have been addressed. They would have a horrible and distressing time.
Ofsted have been expressing their considerable concerns about "off-rolling", where schools find ways of getting children off their rolls before they can have a negative effect on exam results.
Shouldn't we be just as concerned about this "pre-off-rolling"? Are we excluding children before they have even started their education?