Speech-language pathologists (also known as speech therapists) are professionals who are educated to assess speech and language skills and to treat speech and language disorders. In the public school setting, speech-language pathologists work with children who have articulation disorders, language disorders, fluency disorders, and/or voice disorders when the disorder negatively impacts performance in the classroom.
The American Speech-Language-Hearing Association gives helpful suggestions for encouraging speech and language development at:
http://www.asha.org/public/speech/development/Parent-Stim-Activities.htm