What is the best way for society to invest in the human capital of children?

This is related to some research I’m doing in regards to the US tax code and how it finances higher education.<br><br>I am interested in this topic because often I hear that the safety net for children has been a failure (e.g., Head Start), yet we are constantly raising funding for K-12 education. It seems that there is limited research on this topic and I’m wondering if anyone has any thoughts.