Some time ago I read about this topic. Here in Mexico many people believe they or their children are learning English as a second language, but in reality they are not. I guess one learning English in an English-speaking country, will be in touch with English even beyond the language classroom. I think that's the core of a second language, the interaction with Native speakers of English, the context and everything within an English life style. On the other hand, when Spanish speakers in Mexico, which is my case, learn another language at school, like English or French, then they will be learning a foreign language. They go out of the classroom and have no need to speak the target language but their mother tongue, besides there is little or not sufficient English clues around to be in touch with to continue practicing. Of course, it might depend on the context and the situation the learner has.