would have proven immeasurably challenging. Phil and Irene, "Thank you!" I would also like to thank Dr. Lisa Osborne who has always shown kindness, encouragement, and support. Through association with each of you, my life has been enriched by your company.I extend my gratitude to all the participating schools, too. Without the generous cooperation of the schools' Head Teachers, Deputy Head Teachers, class teachers, administrative personnel, parents/guardians, and pupils, the pages within this thesis would have remained forever blank.The research path was made easier thanks to Professor Jaynie Rance and the excellent School of Psychology PGR Academy whose annual conferences provided a wonderful opportunity for me to present and talk about my research and answer attendees' many and varied questions. This was great practice ahead of thesis defence.I would also like to express my sincere thanks to Dr Ceri Bradshaw and Dr Jennifer Gatzemeier for their detailed and informative presentations regarding qualitative analyses.Gratitude is extended to Katie Retallick, also, who kindly facilitated the Welsh translation of the questionnaires. In this respect, I offer my thanks to Swansea University's Welsh Translation Unit for conducting the translations. I remain indebted to Professor Howard Giles, Distinguished Professor U.C. Santa Barbara, United States, who provided guidance with respect to the Welsh language's ethnolinguistic vitality. Finally, for personally clarifying one or two theoretical aspects regarding structural equation model analyses, I remain indebted to Associate Professor James Gaskin, Brigham Young University, United States.Without my parents and family, I am nothing, and in all matters of life, support, and opportunities I owe them everything.