This box of mathematics materials from the Shell Centre on Problems with Patterns and Numbers has become an influential book on the teaching of problem solving.
Problems with Patterns and Numbers focuses on non-routine problem solving in mathematics, and the teaching strategies needed to handle it in the classroom. It is aimed at the upper half of the ability range and ages 13-16, but is more widely applicable with some adaptation.
The classroom materials, covering three to six weeks work, provide close detailed support for the pupils (and the teacher) in the initial stages: this is gradually reduced as they become more experienced until they are in a position to tackle a wide range of unfamiliar problems and assessment tasks on their own. Most of the problems have both spatial and numerical aspects. There are five short chapters on aspects of tackling problem solving in the classroom, including a question marking exercise.