Function is a basic concept of mathematics, in particular , mathematical analysis. With an appropriate development of a function approach, it becomes possible for students to use function models to describe mathematical and non-mathematical problems. After an analysis of the function concept development process, I propose a model of rule following and rule recognition skills development that combines features of the van Hiele levels and the levels of language about function (Isoda, 1996). Using this model I investigate students' rule following and rule recognition skills from the viewpoint of the preparation for the function concept of sixth grade students (11–12 years old) in the Ukrainian education system.