Mathematics learning and practice in school and out of school differ in some significant ways which are explained by the fact that: (1) problem in everyday situations are embedded in real contexts that are meaningful to the problem solver; and (2) the mathematics used outside school is a tool in the service of some broader goal. This paper discusses research which examined mathematics practice in everyday work situations by comparing in-school and out-of-school practice. It presents a framework for gaining insight into the interplay between socio-cultural and cognitive developmental processes through the analysis of practice. Discussion of the research illustrations includes goals of the activity, conceptual understanding, and flexibility in dealing with constraints. Suggestions for teachers in connecting in-school with out-of-school experiences are given. Contains 25 references. (MKR)