In 1999, a non-government school with a long tradition of 'boys only' education in South Australia introduced co-education at the secondary school level. The following year, girls were admitted at the primary school level. Educational achievement and perceptions of the psychosocial climate of the school's learning environment were measured in all primary and secondary students at the end of this momentous year and again one year later. Questionnaires measuring students' perceptions of the relationship dimensions of cohesiveness, friction and satisfaction and the personal dimensions of competitiveness and difficulty were administered, together with a test of achievement. Interesting differences were found in student achievement and perceptions of the school's climate, over time and across the grade levels
