How many current itinerant teachers of the deaf do you regularly meet with. I have one friend in Lincoln Nebraska, one in Iowa, one in Wisconsin, two in St. Louis, and one in Minnesota. These are good friends who I chat with at least monthly. We went to school together and have know each other for years. I also have friends who work in private schools including some in Illinois, Indiana, Seattle, St. Louis, and San Antonio. We are part of a collaboration cohort that fields difficult cases together and regularly meet for mentoring. I am far from the only person with successful students. Perhaps if you are only seeing students struggling, you need to look at where those professionals are and the services they are providing.
I recommended the places I did because I can confirm that they do an excellent job. The mother can continue to provide sign language to a child that attends those schools. I cannot recommend other programs because I can't be sure they provide high quality intervention.