One of the main reasons I wanted to study abroad in Spain was to practice and hopefully perfect my Spanish. In my mind the complete immersion would magically allow me to become fluent. After spending time at Colegio I have come to realize that yes immersion is helpful but the most important aspect of language fluency is how you are taught.
My students are docked "points" if they speak in Spanish during an English lesson. They are constantly told that this is for your future. If they complain or are annoyed about a test or memorizing more vocabulary the teachers remind that this is what it takes to become fluent. The entire mentality is very different from the U.S. Here English, or French or Germany is taught as a second language--adding to their Spanish. In the U.S., generally, Spanish or French is taught as a foreign language. A language that might be useful to know some words should you travel there but always knowing that English will be your back up.
Overall this follows the philosophy of education that I have observed in Spain (or at least in Madrid). Education is a priviledge. Education is the job of the students. Education will depend on how much effort you put in. There is less micromanaging and the students by and large are very mature and self-motivating. There are less excuses made for the students and by the students.
For example, student B, in my fifth grade class, did not complete the English exercises from the week before. I anticipated that he would have created a story but instead he simply looked the teacher right in the eye and said "I did not do it. I am sorry, next time I will be sure to do it." The teacher responded with "Well I am disappointed. This will affect your grade. Do not let it happen again". There is almost a coldness to teaching but that doesn't diminsh the care the teachers feel for the students.
Comparing the teaching philosophies and expectations of Colegio and BPS is interesting and leds me to wonder what would happen if we implemented aspects into BPS, namely the addivitive bilinugalism.