Makes sense. So 2 issues then remain: 1. On a theoretical level, you'd have to show through assessment that the student's rate of learning (or overall level of learning) in a particular area (e.g., reading) is lower for a given level of second language acquisition. Maybe there's an assessment that does this? Not sure. 2. Even if you could find such an assessment, sounds like you still wouldn't be able to use it as the regulations for assessment are what they are.