The "School of Rock" star, who also fronts rock group Tenacious D, has been trying to teach music to his young sons Sammy, nine, and Thomas, seven, but doesn't think he has the right temperament to pass on his knowledge, reported OK! magazine.
"I've been trying to teach my boys how to play instruments but I've discovered I'm not a very good teacher. It takes a certain patience that I don't know if I'm gifted with."
The 46-year-old actor - who is married to musician Tanya Haden - is a devoted father and would rather skip a night out to spend time with his boys.