This article explores how the development of mother-tongue instruction (MTI) policies in the Danish welfare state have created varying notions of difference and sameness in the schooling of migrant students and how they experience these notions locally in practice. Based on an analysis of MTI's policy history and oral history interviews with former migrant students, we analyse MTI policy development within the Danish welfare state as a primary case and discusses whether these developments seem to be unique to the Danish welfare state by considering (West) Germany, the Netherlands and Sweden as a comparative perspective. Noting the paradoxes and dynamics of the welfare-state policy of 'school for all under one roof' at the intersections between the policy and practice level, we posit that migrant students are regulated as a homogeneous group that is expected to be 'the same' but is simultaneously considered to be 'different' from other, majority students. The findings thus reveal the paradox of welfare-state education policies and practice: while macro scale policy for migrant education aims to emphasise difference through MTI, the social consequences at the micro level show the opposite; namely, that MTI produces feelings of sameness and belonging among migrant students.