Scaling up changes everything. How can we predict its effects?
Policy makers at all levels know what it’s like to watch a scheme that’s have done well at pilot stage fail to succeed when scaled up. What works for 30 children in Loughborough may not work for 1000 in Lagos. Or even London.
That’s not because the ideas were poor in the first place, or because the pilots themselves were poorly run, but because scale affects projects in different ways and as such needs a different evaluative approach.