The PEIM (Instructional Developmental Programme for Mathematics) is an intervention model that has its roots in the socio-cognitive constructivist approach. In this model the specific mathematical development of each student beam great weight. Essentially, it has four intervention pillars that constitute the basic ingredients of the complex teaching-learning process taking place in the classroom: students, teacher, curricular contents, and classroom dynamics. Regarding students, the aim of intervention is mainly 1) that all learners in the classroom show a clearly constructivist profile, i.e., that they are both physically and mentally active, and 2) that students are autonomous in the construction of mathematical knowledge. With respect to the teacher, intervention, if neressary, will attempt to fit a constructivist teacher profile: to be proficient on the basics of this approach and on the development of specific mathematical content in the child, showing a positive attitude to mathematics. Intervention regarding contents taught in the classroom will focus on two important aspects: content selection and sequencing. In content selection it is necessary that, on the one hand, priority is given to accomplishing tasks in the class such as reasoning, thought, problem solving; representation. decision taking, carrying out operations, etc., and on the other, that there are fewer memory and mechanical activities. Likewise, there tasks should be significant, both front a psychological and a socio-cultural point of view. Sequencing refers to the need to organise mathematical contents depending on the difficulty that they present to the children. Finally, the aim of classroom intervention is that both students' and teachers' role fits the constructivist model, paying less attention educational resources based on repetition and reinforcing cooperative learning in the classroom.
