Practice is the first line of respect. A bargain struck between teacher and student: I'll teach if you promise to practise. If you do, even just a little, then at each lesson you'll give something. If you don't, if you fail to uphold your end of the bargain, then you can only take because you have nothing to give. The teacher will always know, even if they don't mention it or acknowledge it to themselves, because the energy the student develops by facing the pain of practice is felt most distinctly by the teacher as a jolt which shocks them into full teaching mode. Without this stimulant all the teacher can do is go through the motions, use the lesson for their own benefit, and take your money. What they should do is tell the lazy student what they think of them and maybe suggest another discipline, because by agreeing to teach, even seemingly, under such circumstances, they become lazy themselves.