This study aimed to demonstrate the value and psychometric qualities
of an instrument that assesses social competence for children in critical social
situations within the relationships with peers in the school context - Socially in
Action-Peers (SAp) using CFA and SSA. This instrument was administered to
182 Portuguese children aged between 8 and 11 years, of 3rd and 4th grades.
These children were assessed by three sources: themselves, their peers and
their teacher. Additionally, we used the Test of Emotion Comprehension (Pons
& Harris, 2002; Pons, Harris & Rosnay, 2004) to assess SAp’s criterion-related
validity. Mean differences results in SAp by gender were analyzed. Concerning
to gender, we only have found gender significant differences in a few items and
in the general assessment made by teachers, in which girls being considered
superior. The results of the SAp’s psychometric analysis are satisfactory, both in
terms of items’ sensitivity and reliability (internal consistency) in three versions
(self-assessment, peer and teacher). Finally, we performed a confirmatory factor
analysis that confirmed that the model underlying the instrument’s rational: a
hierarchical model with a 1st order factor (composite social competence) that
has three factors of 2nd order (consisting of the three sources of evaluation: self,
peers and teacher).  Besides the CFA data were analyzed through Louis Guttman’s
SSA - a non-metric multidimensional scaling (MDS) procedure. CFA and SSA
confirmed the psychometric qualities of SAp and identified the subscales and
dynamic relationships between them. Implications of these findings for social 
competence assessment and intervention in childhood are discussed, as well as, the 
advantages and disadvantages of CFA compared to SSA for empirical validation
of psychological constructs are examined