The article demonstrates how a questionnaire gauging students' experiences of participation in decision-making at their school can operationalise student participation in a whole school approach (WSA) to education for sustainable development model. Some 902 students in three upper secondary schools participated in the study by giving their answers to Likert-scale items developed to tap into their experience of participation in the decision-making at their school. The students identified four distinct pathways of participation: (i) School and Leadership, (ii) Teaching and Learning, (iii) Community Connections, and (iv) Student Council. The results are discussed in the light of focus group interviews with eleven of the participants. The student WSA participation questionnaire proved to be a reliable and valid instrument that, together with the student WSA participation model, can be used by school leaders wanting to increase student participation, and by researchers investigating student participation throughout the whole school.