[dragonwriter]

> The tricky thing is, if you let anyone just choose not to pay, there will be plenty of people who are capable of paying who don't bother.

So what? Assuming you have a progressive tax system in the first place, the people that are capable of paying are, in fact, actually paying for the service in any case. Why charge them again?

> So as long as you're going to charge for lunches, you need to have some kind of enforcement mechanism.

Yes, and one of the reasons for free universal public programs paid for by progressive taxes are often better than means-tested programs is that enforcement isn't free (and neither, in the case of school lunches, is handling money for payment for the people that your means-tested free lunch program now means are required to pay for the service) so you end up spending a whole lot more between payment processing and eligibility verification and enforcement than you save by excluding the people actually paying for the service by higher taxes from receiving the service.