A large empirical evidence shows that on-the-job training paid by firms is mainly directed towards high educated workers. In order to explain this phenomenon, we propose two simple models adopting the assumption that education has a positive influence on the efficiency with which individuals acquire new skills. The first one considers an adverse selection mechanism which affects mainly high-educated workers. This compresses their wage structure, encouraging firms to train them. The second model starts from the assumption that high-educated workers are more involved in team production, which generates team specific human capital, reduces their turnover, increasing training investments by firms.