Due to the need to provide tools to physical education teachers to assess rigorously the results of their work in the socio-emotional context, this paper presents the design process and validation of a system of categories for assessing socio skills emotional needs of students in lower primary education level, through direct observation in situations of motor game. The results obtained after the logical and empirical analysis of the data show the reliability and stability of the proposed categories. Moreover, the entire process is shown as an example for the development of record instruments that are useful to measure generic skills in real situations. In conclusion, from the rationale on which the work is based, and in view of the results obtained, the observation instrument proposed complies with the aim of measuring the development of socio-emotional competence through detection of attitudes and behaviour in a real educational context.