We analyse the role of private schools in the teachers' labour market. Private schools employ an increasingly-disproportionate share of teachers in Britain, relative to the number of their pupils. Their teachers are more likely than state school teachers to possess post-graduate qualifications, and to be specialists in shortage subjects. Recruitment from the state sector is an important and growing source of new teaching staff for private schools, and a small though increasing deduction from the supply of new teachers available to state schools. Private school teachers enjoy greater job satisfaction, work with fewer pupils, enjoy longer holidays and, in the case of women, shorter weekly hours. Among women, pay is lower in the private sector, which we interpret as a compensating differential. For men, there is no significant inter-sectoral difference in pay. However, for both men and women there is evidence of a substantial pay premium for private-school teachers trained in shortage subjects. (Contains 4 tables, 8 figures and 13 notes.)