Section 23. The commission shall provide to any active or retired employee of the commonwealth who is insured under the commission coverage for expenses incurred in the medically necessary diagnosis and treatment of speech, hearing and language disorders by individuals licensed as speech-language pathologists or audiologists under chapter 112, if such services are rendered within the lawful scope of practice for such speech-language pathologists or audiologists regardless of whether the services are provided in a hospital, clinic or private office; provided, however, that such coverage shall not extend to the diagnosis or treatment of speech, hearing and language disorders in a school-based setting. The coverage provided by this section shall be subject to the same terms and conditions established for any other medical condition covered by the commission.