According to Luhmann, the education system is based on a primary code that distinguishes between conveyable and non-conveyable issues. The code of conveyance is the basal structure of this system. Moreover, as it is based on the intention to educate and must highlight positive outcomes, education also gives relevance to selection. Checking the results of the education system requires selection, which distinguishes between better and worse performances. Selection is therefore the secondary code of the education system, which contributes to constructing an important part of the pupils' careers and therefore to including them in society. Finally, education relies on the classroom interaction as a key factor that compensates the lack of a symbolically generalised medium of communication. Organisation and professionalization are other important features of education.