Families who are likely to move frequently from one country to another during the children’s school years tend to choose an international school so that the children will have some degree of educational continuity regardless of the family’s location.
If you plan to live in Spain for a number of years, you may want to enrol your children in a regular Catalan school.
If you plan to be in Spain for a short while, then return to your home country, you may want to give your children the experience of a year in a Catalan school, or you may want them to continue with the kind of programme they followed back home.
You can find more information in this link.
You can also check the Practical guide for International Schools in Barcelona.