A school can only do so much to offset the negative impacts of poor home-life. Learned helplessness is real and debilitating and it is often learned at home at a young age. I empathize with the tax payers in this area who see above-average taxes for below-average results.
The point is that even if you get those kids even 10% of the way of others, that might be what buys you one less person between bars. Or suffering from substance abuse. Or fueling Ponzi schemes, MLM or cults as a victim. Or living in the streets. Or voting irrationally for the next populist policy maker (in any part of the political spectrum, not being political here).
The moment you renounce to killing all of those who misbehave, you have to accept that these people are going to be your neighbors for the foreseeable future, and so it really pays to take care of the problem as early as possible, because frankly, you'll be spending resources either way.
One kid has access to books and parents who read with them at home every night.
Another kid has no books at home and no learning support after they leave school.
How much is it going to cost to teach each child to read at the same proficiency level?