So we assume that arguments identify a subject in a state of disequilibrium, and that the purpose of argumentation is to return the subject to equilibrium. And perhaps the nature of our jobs contribute to this misconception, because that line of logic is less of an argument, and more of a scolding -- the kind that mollifies everybody and tells them to shake hands and make up at the end of it.
In reality, arguments exist to shake up equilibrium and cause disruption to what we assume to be 'normal'. In a state of equilibrium, there is no argument. Everyone agrees to not rock the boat, to maintain stability, and keep the status quo. Arguments arise when someone is no longer satisfied with the way things are, and raises a ruckus in hopes of making a change. Arguments advance a position to upset an existing balance, instead of forcing everyone back into a state of compliance and conformity.
Our mistake in teaching argumentative writing is in making balance the objective, rather than treating it as a means to an end. Instead, we need to teach that balance is important only so far as we are prepared to knock it all down. Balance is a pyramid of cans in a carnival game stall. Nobody approaches it to admire how well it is balanced. The attraction is to toss a ball at it and watch it explode into bits on impact. And collect the stuffed toy prize after.
Achieving balance is a lot of work, and yes, the effort is appreciated in the writing of the essay. But the fun part is in demolishing the balance which we have worked so hard to build. So, unfairly stacking the argument, as the kids like to do with the 'three points "for", one point "against"' conceit is like the same carnival pyramid of cans being nailed down on their pedestal -- no fun at all since the outcome is a foregone conclusion. So if that's what we're teaching the kids to do, ironically, what we call 'balanced' is ultimately biased from beginning to end.
Perhaps our mistaken approach is what turns off the kids from writing. We make them work for balance, but deprive them of the joy of demolishing what they have so carefully built, and sifting through the remains to find the prize: some discovery that brings a new understanding or insight to the subject of their discussion.
And that would be so much more rewarding for us to read, as well. There's always a sense that a balanced argument feels unfinished or incomplete. Like it's missing a 'so what?". Well, here's your 'so what'.