They have to be specific. What are the variables surrounding the findings about ability groupings. It is good to use the result of research for decision making but we need to be aware of circumstances surrounding the findings of the research. It is similar to using averages and median and other measures that originated from a normally distributed population and then we apply it everywhere and make conclusion. Lydia Tracking is usually defined as grouping students by ability between classes.
Ability grouping involves creating groups within the same classroom.
The tracking research is mixed, with a notable exception. Effects are positive when kids are tracked and the curriculum is altered to match the level of the students. The ability grouping research is generally positive, but of lower overall quality than the tracking research. So the kind of negative effect you're talking about would more likely fall on the poor. However, the evidence on high stakes testing raising the dropout rate isn't very convincing.