This study describes secondary school students’ HIV/AIDS knowledge, attitudes and behaviour and compares these aspects in two secondary schools in Yaounde-Cameroon. One school runs a formal HIV/AIDS education programme and the other does not. Students’ attitudes towards people living with HIV/AIDS (PLHIV) and trusted sources of HIV/AIDS knowledge are examined. 618 students participated in the survey. The findings indicated that students in two schools were knowledgeable about modes of HIV prevention and transmission. No differences in attitudes towards PLHIV were observed in two schools. Students of the intervention school reported positive attitudes towards condoms than those of the no-intervention school. Girls demonstrated more discrimination towards PLHIV than boys. The research revealed that HIV/AIDS interventions impact moderate behaviour changes. There is need for vigorous input into the formal HIV/AIDS intervention, targeting specific behavioural aspects and perhaps qualitative approaches to understanding the drivers of students’ attitudes.