This paper studies the association between socioeconomic factors, school characteristics and children's cognitive and non-cognitive development in Cat- alonia. We find that children born later in the year, close to the December 31st cutoff date, persistently tend to have lower academic results than those born in the first two quarters. However, we do not observe any difference in non-cognitive development by quarter of birth. The analysis also shows that children who ever attended nursery school do generally better than those who first started at pre-school (P3) or later. Furthermore, we find that fam- ily structure matters since children raised in non-nuclear and low educated families tend to underperform others at school. Estimates also indicate that first generation immigrants, especially Africans, have worse academic perfor- mance than those born in Spain. There seem to be strong benefits associated to time spent reading and studying languages, computer science and music. Finally, there is inconclusive evidence that students who arrive late in the academic year and those with special needs generate negative peer effects in the classroom.