This paper uses a new measure of human capital that works much better in explaining productivity in OECD countries compared to earlier measures of human capital to investigate the educational policy drivers of human capital. A novel methodology is utilised by interacting educational policies, for which time series coverage is very poor, with time-varying core drivers of human capital such as public spending on education. In such a framework, policy effects can only be assessed indirectly as they amplify or attenuate the effect of education spending on human capital. The results suggest that higher attendance at pre-primary education, greater autonomy of schools and universities, a lower student-to-teacher ratio, higher age of first tracking in secondary education and lower barriers to funding to students in tertiary education all tend to boost human capital through amplifying the positive effects of greater public spending on education. Benefits from pre-primary education are particularly high for countries with an above-average share of disadvantaged students. School autonomy yields high benefits especially in countries where schools are subject to external accountability.