Luxembourg's education system is trilingual: the first years of primary school are in Luxembourgish, before changing to German; while in secondary school, the language of instruction changes to French. Proficiency in all three languages is required for graduation from secondary school, but half the students leave school without a certified qualification, with the children of immigrants being particularly disadvantaged. In addition to the three national languages, English is taught in compulsory schooling and much of the population of Luxembourg can speak English. The past two decades have highlighted the growing importance of English in several sectors, in particular the financial sector. Portuguese, the language of the largest immigrant community, is also spoken by large segments of the population, but by relatively few from outside the Portuguese-speaking community.