That's weird because 2 years of one-to-one study with their parent should matter more than whatever method, also teachers don't just go and give up their method

That's weird because 2 years of one-to-one study with their parent should matter more than whatever method, also teachers don't just go and give up their method, even for good reasons. And 2 years of one-to-one study with their parent being effective is not a legit reason to change methods.