The word thing can be a stimulant and also can be a form of echolalia....it may have started by immediate repetition but now be delayed echolalia, my son also has many words and sounds he says over and over. Some are little sing song noises (be-back-a-ewe-ya) he echoed from a peer in third grade and continues to sing daily on and off.
Echolalia and verbal stims can be a symptom in people on the spectrum. (Other conditions too).
The law mandates positive behavior interventions. First step is to try to find out what the behavior is communicating, or what the function of the behavior is. To do that it's standard to do a functional behavior analysis. This term can vary a little. The FBA first defines the behavior of concern, then it is documented in different ways including observations and interviews with you and teachers....and other significant people (day care, docs, etc). The behavior plan then should be designed to reach Appropriate functional behaviors which can replace the negative behaviors.
So, you can ask to have a functional behavior analysis done. Just like any evaluation, put the request in writing and get a receipt so deadlines for responses and completion can be monitored.