Particle models of matter are widely recognised as being of fundamental importance in many branches of modern science, and particle ideas are commonly introduced and developed in the secondary school curriculum. However, research undertaken in a range of national contexts has identified significant learning difficulties in this topic, and suggests that notions of particles that match scientific models are generally only attained over periods of some years. The implementation of a National Curriculum in Science in England was followed by increasingly prescriptive guidance to teachers. This culminated in a framework for teaching lower secondary science, which identified 'particles' as one of five key ideas for organising teaching and learning of science to all 11-14 year olds. In this curriculum context, a basic particle model is introduced at the start of secondary education, and consolidated by being revisited in various contexts over 3 years. However, National Tests suggest that only a minority of pupils attain levels of understanding matching target knowledge. The present paper reports an interview study that explored how a sample of English secondary students explained phenomena commonly met in school science. It was found that students generally used the notion of particles, although most of their particle-based explanations reflected alternative conceptions that have been reported in previous research. It is concluded that a curriculum strategy of early introduction and regular application during the early secondary years is not of itself sufficient to support the desired progression in thinking with particle models, and more sophisticated research-informed pedagogy is needed.