An increase in human capital causes economic growth is unclear, owing to the problems pertaining to the estimation of quantifiable relation between the two. Educational yardsticks like years of schooling, teacher-pupil ratio, enrolment rates etc. may not reflect educational quality accurately. Whereas, human capital measures may show convergence between developing and developed nations, however, there's no empirical evidence to prove income per capita convergence.
Hence, education may improve, but cannot guarantee similar progress in real income across different countries.