Engaging adolescents in changing behaviour (EACH-B): a study protocol for a cluster randomised controlled trial to improve dietary quality and physical activity by Strömmer, S, Barrett, M, Woods-Townsend, K, Baird, J, Farrell, D, Lord, J, Morrison, L, Shaw, S, Vogel, C, Lawrence, W, Lovelock, D, Bagust, L, Varkonyi-Sepp, J, Coakley, P, Campbell, L, Anderson, R, Horsfall, T, Kalita, N, Onyimadu, O, Clarke, J, Cooper, C, Chase, D, Lambrick, D, Little, P, Hanson, M, Godfrey, K, Inskip, H, Barker, M