Quality requirements of curricula are analysed in terms of the educational effectiveness of their implementation. Improvement of educational effectiveness is seen primarily as taking place by improving the pupils' opportunity to learn, by increasing their time on task, by structuring and pacing their instruction, by clear and explicit objectives and by evaluating, feeding back and reinforcing their learning achievements. Education of minority students in the Netherlands and the quality of curricula for their education are analytically evaluated and discussed in terms of these elements of educational effectiveness. Evaluation, feedback and reinforcement, especially, are elaborated as inter-related elements of educational effectiveness, and, therefore, also as inter-related quality requirements of curricula. The analysis has implications for educational policy and development at the national and school level. (Contains 37 references.) (Author)