What to do when student’s parents like to compare their child to better students

[ppwwnt]

I have taught one of my 8-year-old student for 1 year whose parents like to compare their child to other student who plays better than him. They requested me to skip step by step teaching methods which definitely take long time to achieve, to play many advanced arrangements as much as possible at very young age instead. I used to explain to them that it’s not a good idea to force this young student to play advanced pieces without basics  plus, I let him try some difficult techniques already and he admitted that he can’t do that but his parents still insisted to let their child play more and more difficult pieces within a short time and kept asking why the other student can play better (which I think he is child prodigy). So, what should I explain to them or should I suggest them to find other teachers who can guarantee that they can make this student play as good as those child prodigies?

[themeandvariation]

Tell them you thoughts - as mentioned,

"I think your other child is a prodigy, and this child
is a normal child, who would benefit from a more gradual (step by step) approach.  I have tried introducing more advanced technique to them, but they cannot do it."

Another thing you might try is abridging a famous tune, or writing something that sounds difficult but is easy to play.
That kid is going to have a bumpy ride (in all kinds of ways) if this need from the parent to compare children persists. 
And if they insist, if it were me, I wouldn't assist in this path of destruction, and tell them:
 'I can no longer teach the child'.