Article History
Received: 20 December 2017
Revised: 19 March 2018
Accepted: 21 March 2018
First Online: 26 April 2018
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.
: Ethical approval was obtained from Glasgow City Council Educational Services, NHS Greater Glasgow and Clyde Research Ethics Service and the West of Scotland Regional Ethics Service (REC:10/S0703/77). Consent was requested from head teachers of special schools before commencing data collection.