2.2. Instruments

Schoolwork engagement was estimated with a short version of the originally nine-item-long Schoolwork Engagement Inventory (EDA) [30] capturing all the three dimensions: (1) absorption (“Time flies when I am studying”), (2) energy (“I feel strong and vigorous when I am studying”), and (3) dedication (“I am enthusiastic about my studies”). It was scored on a six-point scale (0 = “Never” – 5 = “Daily”). The Cronbach’s α reliability for the scale was 0.76, which was somewhat lower than the Cronbach’s α of the original inventory (0.94) [30] but still good. The mean of the three items was used to measure schoolwork engagement per adolescent. Only those participants who answered all three items were included in the analysis, meaning 3.6% were missing.

School burnout was assessed with the Short School Burnout Inventory (SSBI), which was developed on the basis of the nine-item-long School Burnout Inventory (SBI) [33]. The scale used in this survey contained three items measuring all the three dimensions: (1) sense of inadequacy at school (“I often have feelings of inadequacy in my schoolwork”), (2) cynicism toward the meaning of school (“I feel that I am losing interest in my schoolwork”), and (3) exhaustion at school (“I brood over matters related to my schoolwork a lot during my free time”) measured with a six-point scale (1 = “Completely disagree” – 6 = “Completely agree”). Cronbach’s α reliability for the three-item scale was 0.379, and the reliability between item 3 and the first two was especially low and, for one country, even negative (−0.013). However, the Cronbach’s α reliability for the items 1 and 2 was 0.62, which is acceptable although much lower than in the original inventory (0.88) [33], and thus they were used in this study to measure school burnout. Mean of the scores of these two items was used to measure school burnout per adolescent. Only those participants who answered both two items were included in the analysis, meaning 3.2% were missing.

These schoolwork engagement and school burnout measures were used the same way in one previous paper [39]. The shorter versions of the Schoolwork Engagement Inventory and School Burnout Inventory were used in the survey due to lack of space in the questionnaire.

The social network survey used a student directory to ask about the students’ social ties at school, except for Finland where name generator was used. Student directory contained the first names and family names of all students enrolled in the two grades surveyed. The names were coded and listed alphabetically by class and grade. Participants were asked to nominate a maximum of five schoolmates with the question, “Which schoolmates do you prefer to work with or ask for advice, for example on homework or an assignment?” (later labelled “cooperation”). After that, they wrote the corresponding codes into their questionnaire. The social network survey has been described in detail elsewhere [38].

Social network measures were computed at the ego level (student level) and at school network level, where school refers to the students at the two grades included in the survey.

At the ego level, we focused on student position in the network and computed three measures to capture how important or influential a student is in the peer collaboration network [40]:

Social activity (outgoing social ties) measure is the simplest indicator of a student connectivity with other students in their school peer network. It assigns an importance score on the basis of the number of outgoing social ties held by each student. This measure tells us how many outbound links or nominations (out of five asked in the questionnaire) each student had to other students in the network (all students who were registered in the two grades surveyed in the school).

Popularity (incoming social ties) measure is estimated in the same way as social activity, however, we looked at the number of inbound links or nominations. This means that the number of inbound links or nominations (out of five asked in the questionnaire) each student had to other students in the network (all students who were registered in the two grades surveyed in school) was estimated.

Isolated students is measured as the proportion (%) of students in the network (all students who were registered in the two grades surveyed in school) without reported social ties (no nominations in the questionnaire).

At the school peer network level, we focused on the structure of the school peer network composed by all students registered in the two selected grades:

Density of the school network is a ratio of the total number of relational ties (nominations) at each school divided by the total number of potential relational ties at that school. In our case, density is the proportion of the number of student cooperation ties divided by the total possible number of cooperation ties in the student peer network, which corresponds to all possible ties that students registered in the two grades in the school can establish. It is expressed here as percentages. Zero means no ties between students and 100 means that every student has nominated all other students. A dense network at school, meaning more social ties between students, is generally associated with a higher provision of social support, a faster circulation of ideas and innovations, and a higher enforcement of norms [41].

Centralization measure identifies the most prominent individuals in the network, which is those who are extensively involved in social relationships with other individuals in the network. In other words, it assesses the tendency of a few students in the network to have more social ties compared to others. It is expressed here as percentages. Zero means that all students have the same number of nominations and 100 means that one student is the only one to be connected to all other students. Centralization is a measure of inequality in a network and it is generally associated with better coordination and efficiency but lower satisfaction [41].

Clustering is the average density of ties around the egos (individual students). It measures how much an ego’s friends’ friends are also the ego’s friends. It is expressed here as percentages ranging from 0 to 100. Clustering captures the network closure and the overall tendency of a network to be patterned as a small world structure—a network of several small and dense student groups connected to each other by bridges. It is computed as the average density of ties in the ego’s networks. In our study, clustering measures the proportion of one’s schoolmates (with whom one wants to do schoolwork) that are also schoolmates with each other.

School connectedness is a subjective measure of the bonds the students feel towards their school. It is the student’s perception of school climate, and it represents their impression of and relationship with the school, and it is highly related to the social context within which they are involved. School connectedness captures the subjective perspective about the social ties at school [42]. It is estimated with five items: (i) whether adolescents feel close to people from their school, (ii) whether they feel happy at their school, (iii) whether they feel part of their school, (iv) whether the teachers treat them fairly, and (v) whether they feel safe at school, with four options each. According to the students’ responses, a value was given per item as follows: 1 = “strongly disagree”, 2 = “disagree”, 3 = “agree”, 4 = “strongly agree”. Then, a mean value of five items was calculated per student. Next, a group mean value, ranging from 1 to 4, was estimated for each school on the basis of the answers by all participated students. This score was used in the data analysis. The scores between schools ranged from 2.42 to 3.45.

Socioeconomic variables were included in the analyses as controlling variables. The Family Affluence Scale (FAS) was used to measure adolescents’ socioeconomic status (SES) with four questions [43]. Additionally, age, sex, and country were used as controlling variables.