If you express disappointment your still damage their self-confidence in the end so the only difference is that the video is the more extreme case ... 

It isn't the first time that the children got a stash of F's but I'm guessing this is the first time the father had to take drastic measures ...

Yes, but showing dissapointment is not even close to actively punishing them.

And I'm sure that teacher's consistently handing out the F's isn't damaging their morale ?

Regardless there will be many things in life that will lower one's vanity so why avoid it when there are many cases to confront it ? 

Hence why I'm sure the kids don't need their dad punishing them on top of them already receiving bad grades.

You don't need to go look for trouble just because you will face trouble in your life.

The difference is between consequcnes and punishment.

Getting F's is a consequcne.  It is a logical reaction to the work the child has put forth.  What the teacher is sayins is, "If you don't do work, you don't get good grades".

On the other hand, what the father is doing is not a consequence.  He is not showing a logical connection between what the children are doing and the results.   Their hair has nothing to do with their schoolwork.   What he is saying is "if you don't get good grades you deserve to be treated like shit".  

Much different message there.  

I never understood why the American society puts so much focus in school, they treat it as if it was the ultimate answer to all problems. The average American spends years trying to get a worthless piece of paper so that they can work for someone else, without realizing that the answer is to just educate us ourselves so that we can come up with our own individual and unique ideas that way you can work for yourself, and not be stuck in the 9-to-5 routine.

That of course won't happen since we need "worker bees" but it is always nice to imagine a world where everyone is a producer and there is no longer a need for school that way our children could avoid the stress of having to spend all day working on a mache volcano, or wasting their time doing homework for subjects that they aren't interested in.

Their dad pointng out their failings in public with a new haircut is just the cherry on top of the cake ... 

Not severe at all for punishment when there are parents out there by using physical force ... 

These kids didn't go out looking for trouble but in a way they brought it on themselves for consistently being failure's ... 

The two need not be mutually exclusive ... 

Every action has a consequence trivially speaking ... 

Had they not brought back a bunch of F's we wouldn't be having this conversation ...

The punishment was not a consequence of their action.  It was a choice by the father.  All they learned is "hey my dad's kind of a dick".  I'd also imagine the taunting they'll receive from their classmates won't exactly improve their school life.

How do you prove that such was invariant ? 

It was BOTH a consquence AND a choice. Their failure was an inspiration or an influence for the father to humiliate them ... 

How hard was it for them to shape up and get good grades at their age ? The worst part is they didn't even object meaning they full well knew that they were guilty for their own performance!