Parents are typically involved at the beginning (review past couple days and how things have gone, update progress, what worked and didn't work, etc.) and at the end of the session (go over session and performance on goals, discuss homework/carryover activities, etc.). In my experience, the client performs better if the parent is not directly participating in therapy session as the young children I see participate less if the parent is sitting next to them. It works best for most clients if the parents is observing/watching/listening a little bit away from the actual therapy table/area. I do teach parents hand signs/tactile sound cues so that carryover of prompting for speech sounds continues at home.