I don't think simply taking 3 years of a language and getting A's on them means you are "proficient" in a language. That part of your academics goes into your transcript, and says that you did "well" on your foreign language classses. (Most people do take at least 3 years of foreign language in highschool. It DOES NOT mean they are all proficient in at least 2 languages)
Are you able to converse comfortably in that language? For example, I've lived in France for 5 years and can converse comfortably in the language, and I also have a 800 on the French SAT II. I consider myself proficient in French.
This is not about what foreign language you take at school. It's about how comfortable you are using another language as a form of communication. Imagine you did put down "proficient" on the application and your interviewer asks you to say things in Spanish, or worse, to converse in Spanish. If you are unable to communicate effectively, which I think is possible if your classes were simply beginner's level, they will think you lied or manipulated some parts of your application.
(I've actually heard of quite a number of people who said they were proficient in several languages on the app, but got caught in the interview. Needless to say, they didn't get into those colleges)
Think of it like this. If you are proficient in Spanish, if a Spanish person came up to you and spoke in fluent Spanish, you should be able to understand pretty much everything and also should be able to converse.