Despite increasing corporate efforts to hire from more diverse backgrounds, private school alumni remain dominant among the most powerful positions in British society, according to a sprawling new report on social mobility in the United Kingdom.

New data from social mobility charity The Sutton Trust shows that elite schooling remains the surest route to the top of British society, a reflection that corporate efforts to improve socioeconomic mobility at companies have only made little headway.

Efforts include expanding apprenticeship program without degree requirements, switching from filtering candidates by national exam results to looking at their performance relative to their school average, and collecting data on what share of top ranks come from working-class backgrounds.