It’s not defunding education. It’s saying rather than waste money on something unnecessary over here (like free lunches for the wealthy) let’s spend it on something better (like teacher salaries).

If you have a progressive tax system, excess government aid used by wealthy families is more than made up for by the higher tax rates those families pay. In exchange, you end up with programs that are simpler to operate, have less red tape, and have a broader base of political support.

How much higher would their salaries be?

Order of magnitude calculation…

Let’s say there is a 22 to 1 student to teacher ratio. And 20 don’t need the free lunch but you give it to them anyways. Let’s say you’re spending $5 per meal per kid. That’s $100/day. 180 days per school year. $18k per class.

It could be higher, it could be lower. Certainly it’s enough to be out to good use.

The additional subsidy for free lunches in the US currently is closer to $3.60, and you are massively overestimating how many additional free lunches would be consumed. The majority of school lunches consumed are already free. In 2019[1], 20.1 million free lunches were served compared to 7.7 million full price (and 1.7 million reduced price). And even the "full price" lunches are partially subsidized. So even assuming that all of the students in that class are eating school lunches (they aren't; only about 60% of kids do), the difference is more like 5-6 "unnecessary" lunches, not 20. The real number would likely be significantly lower than that.

[1]: https://www.fns.usda.gov/pd/child-nutrition-tables