To structurally promote a healthy lifestyle among students, an increasing number of Dutch primary, secondary, and secondary vocational schools have obtained the Healthy School (HS) program certificate [
1]. To date, however, limited scientific knowledge is available on the effectiveness of the HS program. Previous studies mostly focused on the short-term effects of initiatives belonging to one of the pillars (health education, school environment, referral, and school policy) within a specific health topic (nutrition, physical activity, well-being, smoking, alcohol and drug prevention, relationships and sexuality, physical safety, environment and nature, and media literacy) [
2‐
4]. Additionally, for these national and international studies, it is difficult to draw unambiguous conclusions about the effectiveness of (initiatives similar to) the HS program [
5,
6]. This can be partly explained by the limited understanding of the factors, characteristics, and processes, i.e., the conditions, that strengthen the implementation and intended outcomes of the HS program [
5‐
7].
Conceptual framework
The conceptual framework distinguishes three levels, namely that of the student, the school, and the region. The school and the region are considered to be so-called complex adaptive systems [
7‐
15]. This means they are systems made up of many components, which are constantly interacting with each other. These components include the people in the system (the actors) and the factors and characteristics of the system. Changes in one part (e.g., implementation of an HS initiative) lead to changes in other parts or are resisted, in an effort to stay balanced as a whole [
8,
12,
14]. For this purpose, there is constant feedback between the components [
12]. This process is unpredictable since small efforts may have large effects and vice versa [
8,
14]. Therefore, in each system, i.e., in every school or region, there is a unique context [
7‐
14]. Based on this theoretical vision, (the preliminary version of) the conceptual framework provides a visualization of the expected process of professional support at the regional level, its implementation at the school level, and outcomes at the student level (Fig.
1).
The school is central to the framework and is visualized by the circle in the middle. The lower part represents the implementation of the HS program, as part of the context of the complex adaptive school system. The upper part shows the actors, factors, and characteristics of the school context that are important for implementation of the program. Circular arrows indicate continuous feedback between the two parts to keep the school system in balance [
7,
16]. The wavy line in the school system shows that there is no strict boundary between the parts, but that they flow into each other (for example, when an HS activity is organized by a group of teachers). Actors in the school context include teachers, students, parents, management, and care coordinators. Relevant factors may be directly related to these actors (e.g., students’ work ethic or teachers’ pedagogical competencies for the HS program), but also to the school as an organization (e.g., the number of hours available for the HS program and coordination by management) and the sociopolitical environment (laws and regulations regarding HS) [
16]. In addition, general school characteristics (e.g., school size) and, if applicable, HS program characteristics (e.g., which topic certificates have been obtained) determine the school context [
17].
The PHS region is shown at the top of the framework. It is assumed that the implementation process of the HS program in schools does not only depend on factors in the school context, but also on the professional support schools receive [
18‐
21]. Top-down input from the national HS program, consisting of financial and practical support, enters the complex adaptive PHS regional system. This reaches the school through an HS adviser from the PHS or directly via the website [
22]. The lower part of the regional system shows the level of support that has been offered to schools. The upper part shows the actors, factors, and characteristics of the context. Circular arrows again indicate constant feedback between these two parts to maintain balance in the system. The wavy line shows that the parts overlap (for example, when a PHS professional supports a school). Furthermore, the overlap between the regional and school systems assumes reciprocal influence between the regional support and the school context, represented by circular arrows. Actors in the regional context include the PHS, municipalities, Youth Health Care Services, local sports companies, environmental organizations, and addiction prevention. Four categories of contextual factors were selected based on existing literature [
18,
23‐
25]. These are factors related to the professional (e.g., attitude toward HS program support), the organization (including available hours for support), the broader context (e.g., shared vision on regional prevention policies), and the collaboration (e.g., method of communication). The regional context is also determined by general characteristics (e.g., the number of collaborative partners) and HS-related characteristics (e.g., the year of adoption of HS program support).
The framework further assumes a relationship between the HS program and student-level outcomes. Indicators of these outcomes are based on the objectives of the program: 1) healthy lifestyle, 2) health and personal development, and 3) educational performance and school absenteeism [
26]. This is shown in the bottom section of the framework. It is hypothesized that the HS program is associated with lifestyles related to the topics of the program, including fruit and vegetable consumption, physical activity, substance use, and sexual risk behavior [
6,
27]. This might in turn improve general and psychosocial health [
28‐
30]. Previous research further demonstrates that unhealthy lifestyles and deteriorated health may be associated with poorer educational performance, such as lower grade point averages, increased likelihood of grade repetition, and school absenteeism [
2,
31‐
33]. Therefore, it is hypothesized that the HS program also leads to improvements of the other indicators via improvements in lifestyle [
6,
26,
29,
33]. This is a complex process of reciprocal influence on lifestyle, health, and educational performance that is shaped by the home, the school, and the broader environment [
34‐
36]. This reciprocal influence is represented by circular arrows between the three indicators. In addition, the impact of the HS program at the student level may vary by school, in part due to differences in HS program implementation [
37]. However, even schools that implement the program in similar ways may vary in outcomes, as these may also be influenced by the factors in the school context described earlier [
38,
39]. The impact of these possible moderators is visualized by the arrow on the left side of the framework.