The World Health Organization defines adolescence as the ages between 10 and 19, emphasizing that supporting both the mental and physical health of this age group is crucial for determining the individual's future quality of life. Problems such as stress, anxiety, depression, maladjustment, substance use, and sleep disorders faced by adolescents can negatively affect the development of healthy lifestyle behaviors.

In this context, students living in boarding school settings represent a more vulnerable group in terms of the need for psychosocial support, as they live away from their families. Boarding students experience difficulties in adaptation due to homesickness, lack of social support, academic pressures, and a strictly regulated lifestyle, and this situation directly affects their health behaviors.

In this study, the effectiveness of a psychosocial adjustment program will be evaluated with intervention and control groups formed on a voluntary basis from ninth-grade female boarding students studying at two public boarding science high schools located in Antalya, Türkiye. The intervention group will participate in a psychosocial adjustment program developed by the researcher, consisting of five sessions, while the control group will not receive any intervention. The program includes structured and interactive group activities on themes such as adopting healthy lifestyle habits, stress and anxiety management, social support, sleep hygiene, effective communication, academic adjustment, and emotional relaxation.

The data will be collected in three phases as pre-test, post-test, and follow-up test; the data collection tools will include the Personal Information Form, the Health-Promoting Lifestyle Profile II (HPLP II), and the Sleep Deprivation Scale for Children and Adolescents. The data will be analyzed using the SPSS program, and depending on normal distribution, parametric or non-parametric tests will be applied. The effect of the intervention will be measured with Cohen's d to calculate the effect size. This study holds original value as it develops a school-based intervention model under the leadership of a school health nurse, and it may provide an innovative contribution based on a holistic nursing approach to adolescents by taking its place among the limited psychosocial intervention studies conducted in boarding school settings.

Inclusion criteria Being newly enrolled in the ninth grade Residing in the school dormitory as a boarding student Having a parent/guardian signed informed consent form Not having any absences during the research process Exclusion criteria Those who have not given voluntary consent

The primary reason for including only female students in the study is to ensure access to the sample group and to maintain the homogeneity of the sample. At the school where the study will be conducted, the girls' dormitory is located very close to the school building, allowing some sessions of the psychosocial adjustment program to be conducted regularly and uninterruptedly after school or in the evening. In contrast, the boys' dormitory is situated at a considerable distance from the school, which would create significant limitations in terms of transportation, safety, and time management for ensuring regular participation. Additionally, due to gender-specific psychosocial developmental differences during adolescence, selecting a homogeneous sample will facilitate the adaptation of the intervention program content and allow its effectiveness to be evaluated in a more controlled manner.

The study was conducted with adolescent participants, and to protect participant confidentiality, IPD (Individual Participant Data) sharing is not planned.