On concept of function at Middle Years Programme school in Espoo
School in Espoo, Finland, follows the Finnish national core curriculum but approaches teaching according to Middle Years Programme. The language of instruction is English. Material for teaching functions that would fulfill these criteria is not readily available. Therefore, such material was tailored especially for the needs of the school. The development of the material led the researcher to ponder, how students eventually grasp the idea of function and how the concept of function should be approached in teaching in the future. The data was gathered in spring 2012. Out of 63 ninth graders in the school, 49 participated in the study. A research on the concept of function by Vinner and Dreyfus (1989) was used as the source of inspiration for this study. The definitions of function among lower secondary school students were compared to similar data gathered among upper secondary school students during the same spring. Both qualitative and quantitative methods were used in the analysis of the data.