January 6th is "el Día de los Reyes Magos" or Three Kings Day in Spain and Latin America, and it is a big celebration. As the tradition goes in these countries, it is the three kings (and not Santa Claus) that bring gifts to the children.
Also typical of this holiday is the round sweet bread the students are eating. It's called "Rosca de Reyes". (They are also drinking Mexican hot chocolate.) Inside the bread is a bean that represents the baby Jesus. The person that finds the bean has to host the next party!