Help - I would be grateful for feedback

I am involved in a situation where the special Ed TA has been teaching the same special needs student for 5 years.  I understand that is a bad idea but can't find any resource materials concerning this issue.  My concerns, among other things, is that the child has become dependent upon the one TA.  Equally I am concerned the TA finds this a challenge to be with one child for so many years.  Can anyone provide feedback ?