Despite the significant increase in the Portuguese mathematics literacy scores for PISA (Marôco et al., 2016a; OECD, 2016), TIMSS 4th grade and TIMSS advanced (Marôco et al., 2016b; Marôco et al., 2016c; Mullis et al., 2016a; Mullis et al., 2016b), the national mathematics exams’ scores do not show the same trend line, as no consistent statistically significant differences between the average results achieved in recent years (GAVE, 2011-2013) can be found. To use LSISA findings and incorporate them in national policies and curricula, concurrent validity of scores from the two set of measures must be previously demonstrated (Hambleton et al., 2009; Lin et al., 2014, Lindblad et al., 2015). We aimed to determine whether the Portuguese mathematics results from LSISA and from national mandatory exams have concurrent validity. We hypothesize that there is concurrent validity between the two measures, which will show regional variations in interaction with the students’ families/average regional ESCS scores. Concurrent validity was assessed by means of a correlational analysis of scores of the national exams and LSISA mathematics literacy for the same cohort of Portuguese students that participated in either TIMSS 4th grade or TIMSS Advanced 2015. Lack of variance explained will be modeled trough HLM of residuals from a linear regression of national exams on LSISA scores with socio-economic and academic predictors. Principal component analysis on residuals will be run to assess the dimensionality of the overall lack of fit results for both the LSISA scores and national exams. Overall, national scores have shown good agreement between TIMSS Math scores and the national Math exams’ scores both at grade 4 (r = .71, p < .001) and at grade 12 (r = .72, p < .001). We expect that regional differences and ESCS will contribute to explain mathematics achievement in the national and LSISA. HLM of residuals on socio-economic and academic variables will help to explain the lack of agreement between national exam’s scores and LSISA scores (50-52% of unexplained variance) after accounting for regional differences and ESCS.

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