Hi, @owasco. Thanks for stopping by. It is complicated, especially in formal settings (schools, universities).
 I always told those students who struggled with the language that the formal setting did not work in their benefit (because the institution tries to standardize teaching and learning). Usually, when those students who were underperforming enrolled in some private course or took a summer trip to, say, Trinidad (the closest English-speaking destination--we are talking about the old good days when a student could afford a three months stay at Trinidad) they learned more and faster. They'd come back to the university program more confident and ready to advance in their degrees.
Some institutions can be very strict in their approach and here's where the role of the instructor is so important: to find alternative methods, materials or techniques to address every student's learning skills and particular situations. A student with a speech impediment, for instance, may fail a phonetic/pronuntiation test in a university or academy, but that does not mean they cannot communicate effectively. That same student/learner can succeed in a different setting.