The assessment instruments used for measuring students engagement is a crucial dimension on students’ engagement research and practice. However, few studies have examined the equivalence of different measures of students’ engagement with school. The objective of this study was to describe the engagement with school in Portuguese middle and secondary students, using two different measures of school engagement - the Student Engagement Instrument (Appleton et al. 2006) and the Student Engagement Survey (SES; National Center for School Engagement, 2006). Participants were 4888 students from 101 Portuguese schools, from 7th and 10th grades. Results revealed that the two measures are correlated and present the same tendencies by gender and by grade. Females and 7th graders are more engaged with the school than males and 10th graders. Furthermore, academic achievement and parents’ education level were positively correlated with students’ engagement with school, regardless of the instrument used. However, in spite of the common tendencies found by the two instruments on the associations with socio-demographic characteristics and with academic achievement, the strength of the correlations varies significantly depending on the instrument used.