ArgumentIn this paper, I argue that studying school textbooks is a fruitful way to investigate mathematical conceptions in different national contexts. These sources give access to the written production of an extended mathematical milieu whose members write for various audiences. By studying the case of late 1950s French and English textbooks issued for a growing audience of 11- to 15-year-old pupils, I show that a plurality of conceptions was projected at the time onto pupils and their teachers in both national (...) contexts. I link this diversity to contemporaneous debates regarding mathematics teaching and argue that textbooks themselves have to be considered as active agents of such debates. (shrink)