The present article analyzes the development of the ethnic gap--with respect to the attainment of vocational degrees--over the immigration cohorts 1960-2001 by examining how social integration indicators and general secondary school education may help to explain the trend. It was found that the gap between natives and migrants increased. Above all, the large increase in the gap over cohorts between Germans and Turks is alarming. In contrast to that the gap and its increase between the group of immigrants from Central-/Eastern-/Southeastern European countries as well as from other former recruitment countries and German natives is comparably small and can to a large extent be explained by a growing gap regarding the level of general secondary education among the newer immigration cohorts and native Germans due to educational expansion and to a growing impact of the secondary school education for the achievement of vocational education. The effect of social integration plays a smaller role compared to general secondary school education and it even decreases over immigration cohorts.