Where young people's upper-secondary education spans work and institutional domains, questions arise about learning across both spheres and its guidance. Theoretical accounts of 'boundary crossing' have explored how vocational teachers can integrate learning across domains by drawing on extended concepts and theoretical knowledge to solve workplace problems; whilst empirical accounts have validated the role of vocational educators by describing the workplace and schools as equally valid, complementary spheres. Different understandings, described here as 'integrative', 'complementary' and 'implicit', appear to reflect different national patterns of vocational education. The paper reports a qualitative study conducted around two case studies, located in Germany and England, of the way vocational teachers' understandings of facilitating learning across domains are constructed. Vocational teachers working in Germany's 'dual training' claimed to provide advanced knowledge that they compared to practical work skills, reflecting 'implicit' or 'complementary' approaches to learning across domains. Teachers in England, where workplace learning elements are more unevenly developed and lack institutional foundations, nevertheless described colleges and workplaces as distinctive, little-connected spheres. These differences suggest that teachers' approaches are less shaped by the potential or necessity for 'integrative' approaches than by the way different systems enable or constrain their conceptualisation of 'possible futures'.