Flanders, the northern, Dutch-speaking part of Belgium, is experiencing growing intraand interlingual diversity. On the intralingual level, Tussentaal ('in-between-language') has emerged as a cluster of intermediate varieties between the Flemish dialects and Standard Dutch, gradually becoming the colloquial language. At the same time, Flanders is encountering increasing numbers of immigrants and their languages. This paper analyses the way Flemish language-in-education policy deals with perceived problems of substandardisation and multilingualism, in order to create equal opportunities for all pupils, regardless of their native language or social background. Both the policy and the measures it proposes are strongly influenced by different, yet intertwined ideologies of standardisation and monolingualism. By propagating Standard Dutch as the only acceptable language and by denying all forms of language diversity, Flemish language-in-education policy not only fails to create equal opportunities, but also reinforces ideologies that maintain inequality. Instead, language policy should be open towards language diversity, taking the role of teachers in forming and implementing policies into consideration.Keywords: language-in-education policy; standard language ideology; monolingualism; social inequality; Dutch in Flanders; Tussentaal Language policy: ideology, planning and practice Language policies are present in some form in all domains of society (Ricento, 2006). It is in the domain of education, however, that such policies have the most impact on the members of society, as language-in-education policies play a paramount role in how a society articulates and plans for the future of its members (Liddicoat, 2013). Official documents are the most overt and articulated forms of language policy, but policies also exist in more covert forms, underlying the practices of language use and language learning in education. As such, policies discuss societal beliefs and attitudes about the value of languages or language varieties: which languages or language varieties are considered to have the most value regarding future societal success for pupils, and subsequently have a place in the classroom? This inextricable link between policy and society is used by Djité (1994) to discern between two kinds of processes in language policy: (i) processes at the societal level, where certain problems (e.g. social inequality) are formulated, together with possible solutions and (ii) at the linguistic level, where the linguistic norms which a community will use (or is expected to use) are selected.