A methodology to empower citizens towards a low-carbon economy. The potential of schools and sustainability indicators by Lizana, J, Manteigas, V, Chacartegui, R, Lage, J, Becerra, JA, Blondeau, P, Rato, R, Silva, F, Gamarra, AR, Herrera, I, Gomes, M, Fernandez, A, Berthier, C, Gonçalves, K, Alexandre, JL, Almeida-Silva, M, Almeida, SM