I am the Vice President of Programs at the Luminos Fund where I oversees the global programs team to support joyful, foundational learning for children at the margins. I started out as a medical researcher before embarking on a career in evidence-informed decision making within the International Development sector. I have specialised in education - and specifically in foundational learning - because I am convinced that solving the learning crisis could lead to truly transformational change.
Great post - glad to see discussion on education on this forum. In case you haven't seen it there is a new report on education from The Life You Can Save here: https://www.thelifeyoucansave.org.au/research/sector-reports/education-sector-report/?utm_source=LinkedIn&utm_medium=Landing+page&utm_campaign=Education+Sector+Report&utm_content=li%2Ctw
Great paper - I love the approach of considering a broader range of impacts together.
On the impacts of schooling versus learning a good paper is https://riseprogramme.org/sites/default/files/2020-11/RISE_WP-049_Kaffenberger_Pritchett.pdf
Re. cost-effectiveness there are examples of very cost effective interventions - see analysis from @Vadim Albinsky above.