Its an interesting point which i have noticed and have been concerned about as well.
However, another problem, which leads to the aforementioned issue, is that almost every student has issues of some sort that requires therapy or other aid that requires more attention than the average student should be receiving which results in attention deficits for the “average student”.
I would suggest that parents who feel their child needs more attention than they are getting, should consistently call the teacher, randomly visit the class, and in general make herself a regular to the teachers. It could backfire and make the student on the teachers “black list” too though… Gotta use good judgement.