that scale is complete bullshit and dont try to tell me otherwise and your reccommendation of size is complete bullshit.anywhere from 170-185 should be fine depending on his ability, what hes skiing, weight, flex, and agressiveness.
First you should find out what ski you want, then the length.
If its strictly a park ski stay 170-175-give or take a cm or 2. If its an all mountain ski go from 175-180. If its a pow/big mountain ski go from 178-185. Again all of this depends on different factors. Just dont go below 170.
If i weighed 150lbs I wouldnt be on a ski smaller than 185. Its all about personal preference. We need more information. What skis did you like?What skis didn't you like? What lengths do you like? What terrain are you skiing? Is this going to be an addition or a quiver or a one ski quiver? Whats your ability? Are you agressive? Are you still growing? If so, how much do you think?
All of that plays a role in ski size, depending on which ski you go with. More information is needed. Any repsonses you got are based off of personal preferences and not for you. If you havent demoed already try to do so. Try out a friends ski. Go to a shop and see if they have demoes.