Many countries have introduced flexibility in their admissions equivalents for tertiary education, allowing students to apply with vocational rather than academic qualifications at upper secondary level. However, entrants with vocational qualifications are generally less likely to succeed at university. Students from disadvantaged backgrounds are also, on average, less likely to succeed: they are more likely to drop out, or graduate with a lower class degree, even when they have the same prior attainment scores and take the same university course. Rich individual-level data in England drawn from administrative records allow us to link outcomes at university with social background and attainment and qualification routes at school, going back to lower secondary level, before academic and vocational pathways diverge. We can thus use the English example to explore whether the relative lack of success of students from low socioeconomic status (SES) backgrounds is in part because they are more likely to enter university with non-traditional qualifications that offer less effective preparation for study. Our results reveal a significant penalty associated with entering university with these vocational qualifications. Controlling for qualification type reduces the SES gradient in dropping out of university by 42%, and graduation with a lower class degree by 28%, although significant SES gradients in success still remain. There is a tension between allowing students from lower SES backgrounds to use vocational routes to enter university and these persistent gaps in university outcomes. Countries using both vocational and academic routes as pathways to university should be aware of this potential conflict.