A method for the analysis of a science curriculum for the levels of cognitive demand that it makes, in Piagetian terms, is described. Examples of the detailed application of this method to the West Indian Science Curriculum are given, and a summary of the demand levels of the whole curriculum presented. A check on the validity of the method of analysis is made both by looking at inter-rater reliability, and also by testing the predictions of success and failure made on the basis of the curriculum analysis combined with pupil assessments. These checks prove to be satisfactory, and the implications of mis-match of curriculum to population are investigated at three levels: the possibility of modifying the curriculum, short term programmes for accelerating cognitive development, and the long term environmental determinants of cognitive growth