This article was downloaded by: [Mari-Anne Sorlie] On: 15 December 2014, At: 11:53 Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Click for updates International Journal of School & Educational Psychology Publication details, including instructions for authors and subscription information: http:/ / www.tandfonline.com/ loi/ usep20 Reducing Threats to Validity by Design in a Nonrandomized Experiment of a School-Wide Prevention Model Mari-Anne Sørlie a & Terje Ogden a a The Norwegian Center for Child Behavioral Development (Atferdssenteret), Oslo, Norway Published online: 12 Dec 2014. To cite this article: Mari-Anne Sørlie & Terje Ogden (2014) Reducing Threats to Validity by Design in a Nonrandomized Experiment of a School-Wide Prevention Model, International Journal of School & Educational Psychology, 2:4, 235-246, DOI: 10. 1080/ 21683603. 2014. 881309 To link to this article: ht t p:/ / dx.doi.org/ 10.1080/ 21683603.2014.881309 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions