It can be frustrating that childless people and people with only one kid wind up subsidizing families with more kids (by way of child tax credits, benefits that are more available for people with more kids, and higher payments for things like public schooling, etc.) Yet, at the same time, we don't want to punish innocent kids by letting them sit in functional poverty just because their parents decided to have a "quiverfull" without an income to afford that without help.
So, here's an idea for a solution: give parents an option of whether or not to claim any benefits for kids beyond the first two (e.g., whether to claim them for child tax credit/welfare purposes, whether to send them to public school, etc.) If the parents opt-in, then they get those things the same as today.... but, in exchange, the parents have their Medicare/SS full eligibility age postponed by 5 years for each such kid.
So, if you want to claim four kids for tax purposes, and send four kids to public school, and so on, that's fine and is your choice. However, you'll effectively pay back the rest of society for your disproportionate take by way of postponing retirement. You'll work until 77 before the government gives you full SS benefits, where most get then them at 67. Want 6 kids? Fine, we'll help out with that, too -- but expect to work until you're 87 (or dead). It sort of takes the form of a loan, where the extra benefits your kids suck up when they're young wind up being partly reimbursed by you in your elder years.
That would discourage people from burdening the environment by overbreeding, but would ultimately leave that decision to the individual. It would avoid punishing the kids. And it would help to prop up SS and Medicare funding.
