Graham Browne seems to be very confused in his understanding of evolution and geological processes.
Firstly, the theory of evolution explains the development and diversity of life on earth. It does not cover how life initially began - that is abiogenesis and is subject to various ideas, none of which have enough supporting evidence to be established as an accepted scientific theory, therefore it is not taught as such.
Secondly, his statement that "conventional evolutionism depends upon the assumption that planetary processes have always taken place at more or less the same speed" displays a complete ignorance of evolution and geology. The term "evolutionism" is not a recognised scientific term and geologists are fully aware that planetary processes can take place very slowly - sedimentation in deep ocean basins, for example - or very quickly, as with catastrophic volcanic eruptions.
What is necessary for evolutionary change is deep time; an earth that is billions, not thousands, of years old.
Should Mr Browne wish to invite young-earth creationism into his school, I suggest that he understands the absurdities of that idea, which include the "fact" that Tyrannosaurus rex did not kill or eat meat, despite its obvious carnivorous dentition, when it lived in the garden of Eden with Adam and Eve; that Noah (aged 600) included dinosaurs on his ark; and that fire-breathing dragons are not myth, but reality!
There is nothing more absurd than young-earth creationism, which is an affront to modern religion. I would also remind Mr Browne that many of those who accept evolution are neither atheists nor humanists. The acceptance of evolution as a scientific fact and theory resides very comfortably with people of the Christian and other faiths - some of whom are even ordained ministers in the Church.
James D Williams, Lecturer in science education, School of Education and Social Work, Sussex University.