You are here » Home » Study Design

How were the ‘PaLS’ schools selected?

The sample of 22 ‘PaLS’ schools was drawn from the Central Clydeside Conurbation, a socially mixed and mainly urban area which includes the City of Glasgow.  Because it was important that the sample was representative of the local population, the school selection process was based on geographical location (within or outwith Glasgow City), denomination (Catholic or Non-denominational) and deprivation (the proportion of pupils in receipt of a clothing grant).  Overall, the 22 (21 local authority and one independent) schools represented 21% of all S4 pupils in the area.  Eighteen of the schools had been involved in one of our previous school-based studies, the West of Scotland 11 to 16 Study.

In order to build up a picture of the peer group structure and each pupil’s position within it, all pupils in the S4 year group within each school were invited to take part.


What data were collected?

Prior to the main ‘PaLS’ survey, a pilot study was conducted in another secondary school, during which S4 pupils and a number of staff members helped with the design of questions, and provided feedback on items about friendship groups and hierarchies.

The main ‘PaLS’ survey sessions took place between January and March 2006. In order to standardise for the natural variation in cortisol l(see the FAQ page for further information) levels throughout the day, all survey sessions took place during the first morning class (beginning around 9.00am and lasting 45-55 minutes). During these sessions, pupils filled in questionnaires about their health and well-being, lifestyles, life at home and in school, and their friendships and membership of groups of friends. Research assistants also interviewed each of them very briefly, asking a few questions about their health, ethnicity and parental occupation; they also recorded their height and weight. Copies of the pupil questionnaire and the schedule completed by the research assistants are available. In addition, each pupil provided two saliva samples, one at the beginning of the session and one at the end. They did this by chewing on cotton rolls (like dental swabs) for about two minutes. The saliva was analysed for cortisol, commonly described as the ‘stress hormone’.

In four schools, a second session was held, during which pupils completed an interactive, computer-administered interview about their feelings and emotions.  We first used this interview (the Voice-DISC) in the West of Scotland 11 to 16 Study; more details of our methodology can be found here. In the Voice-DISC, respondents use headphones to listen to questions read out to them by an interviewer and answer using the keyboard of an individual laptop computer.

Finally, after the survey sessions, interviews with teachers responsible for health promotion / guidance issues and for the S4 year group were conducted in the majority of the schools. These gathered information on each school’s ethos, values and health promotion activities, and provided an overview of the peer structure of the year group.

How many pupils took part?

At the time of the surveys (the 1995-6 school year), there were 3,950 S4 pupils in the 22 ‘PaLS’ schools, 3,194 (81%) of whom completed a questionnaire. Of these, 3,057 (96%) were briefly interviewed and had their height and weight recorded and 2,995 (94%) provided two usable cortisol samples.