This study aims to reflect on the relationship between families’ socio-economic, cultural and religious circumstances and their children’s success at school. We seek to enquire as to how certain conditions of fragility and inequality of some family groups (due to their origin, religious practice, unstable employment and residential status, and low income) affect families’ participation in schools and their children’s educational success. We also discuss whether socio-cultural diversity is a relevant factor for equity and equal opportunities in our society. To do so, we will present some of the results achieved via three studies carried out by the GRASE (Social and Educational Analysis) research group at the University of Lleida (Spain) continuously from 2015 until the present. The results show that cultural diversity and the fragile socio-economic circumstances of some families, despite appearing as being attended to in the discourses of schools, in their practices analysed, are difficult to materialize; this, together with the frailties of centres the selves (due to cut-backs in the field of social provisions and education by the public authorities, overloads in the ratios of public centres, disquiet among teaching staff, etc.) in some cases involves situations of inequity and risks of educational exclusion.