This article focus on the evaluation process of the group of subjects named as “students with mental retardation” in the school context. Through the theoretical contribution of the systemic thinking, this work deals with the dilemmas lived by a group of teachers when they conducted the initial evaluation of the students in the specialized educational services context. As a result of the pedagogical evaluation, we have the decision related to the frequency (or not) of the scholar in the specialized educational services and the insertion (or not) of this pupil into one of the categories of School Census MEC/INEP. This process, there are the tenuous contours between learning disabilities and mental retardation. It must be observed the choice of some teachers to deal with pupils with learning disabilities. Through the scope of this option it´s possible to notice different movements that position the subject, attributing to him a place: students with learning disabilities who do not attend the service; students with learning disabilities who attend the service, but are not inserted in the school census MEC/INEP; students with learning disabilities who attend the service and are inserted in the school census MEC/INEP in the category of mental retardation. And still, it receives important relevance, the distressful weight of the responsibility of attaching a student to the category of mental retardation through the pedagogical action.