I have tried to fit in with people who have their own aircraft or group, it has always been a pain, cant quite put my finger on it but never seems to work as well as the discipline of a school. My latest student who has been flying with group members has extremely bad habits, jump in and go, no wx or notams or planning, radio non existent, its taken me months to get him back on track. He has passed his exams now, related to you all in an earlier post, but I have stated to him if he wants me to continue teaching him he must do this through the school I work for.
I have had constant snipping from his other group members saying Im taking to long to teach him, and he needs to move on to the next stage, nav etc.
I am a mild mannered instructor but just had enough. Cost is always an issue, he gets the ac for 86.00 an hour wet PA28 . He now has to pay 170 dual rate at the school and doesnt like it, but there you are, I am a professional and like to turn out well disciplined and trained pilots, thats not happening using the group ac, too many distractions and non instructors trying to train him.
Sometimes you have to stick to you plan and not bend over backwards for everybody else. Its taken me 10 years as an FI to start practising that principle, but I do stick to it now, if they dont play ball I walk away.