On the face of it, you might at the least want to question the wisdom of making such a strong Christian statement, given that Lady Margaret's population is about half-Sikh and a quarter Hindu, with the remaining quarter divided between the Muslim and Christian faiths.
In fact, he consulted local religious leaders before he finally decided - and was given their support. They foresaw, and he has found, that holding a position of authority within his own faith gives reassurance to families who, whatever their differences, are at one in having religion at the centre of their lives. This has been particularly noticeable as he has managed the school's response to the law on religious education and school assembly.
He felt himself, for example, to be arguing from strength when he secured a dispensation from the requirement to have Christian worship. "We had agreed with all the groups that we would offer a balanced programme that would celebrate all the major festivals of all the major faiths. Consequently, of our 658 pupils, not one is withdrawn from assembly."
On Fridays, Malcolm wears his dog-collar - "the Christian families see a Christian minister wandering about the place. But people also see me in my Christian outfit talking of other faiths."
He is unpaid as a minister, but has pastoral responsibility for Perivale United Reform Church. Although well-supported by church elders, he does find it difficult at times to keep his church work to the evenings and weekends. "There are funerals, for example, though many people have been considerate and died in the school holidays."
There are compensating advantages, however. "Parents will come and talk about things that they might not talk about to another head - bereavement and so on. I always say we give the full service from baptism to the grave."
Being a salaried priest in an urban area is a difficult enough job these days.
To be an unpaid minister - a "non-stipendiary" in some denominations, a "worker priest" in others - demands selflessness and dedication of a high order, and combining the task with being head of a big primary must draw heavily on Malcolm Child's emotional and physical resources.
"I felt I had to do it. I don't know why, because at times I could have done without the hassles. I do know that I've never doubted the existence of God, and my faith helps me to get through whatever life throws. Some people manage without faith, but for me, that's where I'm coming from."