India is yet to achieve the goal of universalisation of elementary education or 100 per cent enrolment and retention of children with schooling facilities in all habitations. Despite the government's attempt to achieve this goal through the Sarva Shiksha Abhiyan, which has a special focus on girl children, students belonging to disadvantaged families still do not attend classes regularly. This paper examines various reasons for poor attendance behaviour of students in formal schools. On the basis of a study in the eastern slums of Kolkata, it finds that retaining the students in a formal school is far more difficult than enrolling them, particularly if the students are from very poor economic backgrounds.