Equal access to education is only a necessary (not a sufficient) condition for justice. Equal access is not equal opportunity. This must comprise equal chance of success. But chances of this kind, on the contrary, are very unequal. The negative correlation between the financial, social and cultural status of families and the opportunity of access to the varying types of education, and thereafter of success, is far from having the same weight in every country, although it remains a universal phenomenon. Children from poor backgrounds Children from poor backgrounds are compelled to go to work prematurely, students who work have to do so in addition to studying. Poor hygiene, inadequate diets, and overcrowded homes hinder education development, and Other equally important causes include cultural conditions (especially language), that determine the level and content of academically useful pre-school knowledge.