I have no power to improve public schools on a timeline where it helps my kids (it will take years, if not decades, to move the needle on outcomes from improving public education institutions; politics, funding, internal systems in school systems and schools themselves). I can and do homeschool today (not by choice, but I felt it was the least worst option based on constraints). If you can’t, I’m sorry the system failed you. Still try to plant trees whose shade you won’t sit in, but if you need shade now, build your own shade.
Donating towards and voting for political candidates who have communicated effective measures of education reform as part of their platform. For what its worth, I'm not really interested in grandkids, so that's not what I'm optimizing for (rather, a high functioning educational system for any child who needs exposure to one, broadly speaking). I am a fan of civilization and contributing to its improvement within my influence sphere.