The book, first published in 1983, explores the argument that justifies mixed ability groupings in schools and the consequences of practicing the different justificatory arguments. The issues to be dealt with by staff making decisions about grouping arrangements in their schools are clearly worked out from basic principles rooted in social philosophy. The ideas of social justice and fraternity, implicit and unexamined in much discussions about mixed-ability grouping are here explained and their limitations and implications described. The issues discussed in this book are not only important for teachers and for those studying to become teachers, but also for school governors, administrators and parents who can gain a better understanding of the school system through this study.