I had speech therapy as a child. I don't remember when exactly - the memories have become quite murky by now, - but I think I was not in school yet, or in grade one, because we were still living at my grandparents' place (we moved when I was around eight years old). At that time I could already speak allright, but I had difficulty pronouncing certain sounds, like the rolling Russian "r" (I made it a guttural "h" sound, what my mother called a disturbingly Jewish pronunciation) or the "l" sound (which I pronounced as "w"). For example, I would pronounce the word "yamki" ("little pits") the same as "lyamki" ("suspenders").
All I can remember is lying on my back on the couch in a dimly lit office. The speech therapist would place some sort of wooden ball on a handle inside my mouth, behind the tongue, and asked me to blow out the air with as much force as I could, so that a resounding "thrrrrrrr" sound would be produced. I had to do it again and again until I was dizzy with hyperventilation. I can recall just lying there and wishing it were over sooner (the sessions must have seemed endles to me), while listening to my mother and the speech therapist chatting energetically about this or that.
The speech therapy did help - I learned to pronoune "r" the proper way, and I started to pronounce "l" after soft vowels, but I still cannot pronounce it after hard vowels up to this day.