The effects and costs of an anti-bullying program (KiVa) in UK primary schools: a multicenter cluster randomized controlled trial by Badger, JR, Bowes, L, Babu, M, Broome, M, Cannings-John, R, Clarkson, S, Coulman, E, Tudor Edwards, R, Ford, T, Hastings, RP, Hayes, R, Lugg-Widger, F, Owen-Jones, E, Patterson, P, Segrott, J, Sydenham, M, Townson, J, Watkins, RC, Whiteley, H, Williams, ME, Stand Together Team, Hutchings, J