Methods

Study design and setting
This was a cross-sectional study conducted among adolescents between 13 and 19 years enrolled in junior and senior private and public secondary schools within the Abuja Municipal Area Council (AMAC) between May and August 2024. This study was conducted in the Abuja Municipal Area Council (AMAC), one of the six area councils of the Federal Capital Territory (FCT), Nigeria. AMAC is the most urbanised area council in the FCT and houses the seat of the Nigerian government. According to the FCT Universal Basic Education Board, AMAC has approximately 287 registered secondary schools, comprising 112 public (government-owned) schools and 175 private schools, with an estimated student population of over 150,000 adolescents.

Sexual and Reproductive Health (SRH) services in Abuja are available through various channels, including school-based health programs, primary healthcare centres, and youth-friendly health centres. The FCT Secondary Education Board mandates a basic Family Life and HIV Education (FLHE) curriculum in public schools, though implementation varies. Private schools often develop their own approach to SRH education. Formal SRH services accessible to adolescents include family planning services, STI testing and treatment, and antenatal care at public health facilities, typically requiring parental consent for minors. However, access is often hindered by provider biases, confidentiality concerns, and limited youth-friendly service points. Community-based organisations also provide some SRH outreach programs, though coverage remains limited.

Sampling procedure
A multistage sampling technique was employed to select study participants:
Stage 1 (Selection of schools): All secondary schools in AMAC were stratified into two strata based on ownership: public (government-owned) and private schools. Using a computer-generated random number list, 4 public schools and 4 private schools were randomly selected from the sampling frame obtained from the FCT Universal Basic Education Board. This ensured representation from both school types proportional to their distribution in the area.
Stage 2 (Selection of classes): In each selected school, a complete list of all classes (from JSS1 to SSS3) was obtained. Using simple random sampling (balloting method), two classes were selected from each school, one from junior secondary (JSS1-3) and one from senior secondary (SSS1-3) levels, to ensure representation across grade levels.
Stage 3 (Selection of students): All eligible students present in the selected classes on the day of data collection were invited to participate. For students who were absent, replacements were randomly selected from the same class on subsequent days until the required sample size was achieved. This approach minimised selection bias while ensuring adequate representation across age groups and class levels.

Sample size and study population
The sample size for this study was determined using the Cochran formula for descriptive cross-sectional studies. Based on a 95% confidence.  level (Z=1.96) and a 5% margin of error (d=0.05), the calculation utilized a prevalence rate (p) of 78.8% (0.788). This prevalence represents the known level of good contraceptive knowledge among adolescents in the Federal Capital Territory, Nigeria [10]. The resulting minimum required sample size was calculated to be 257 participants.

$$
n = \frac{Z^{2} \cdot p \cdot q}{d^{2}}
= \frac{(1.96)^{2} \times 0.788 \times 0.212}{(0.05)^{2}}
\approx 257
$$

However, due to logistical constraints and school access limitations (including restricted school days, ongoing examinations, and the need to complete data collection within the school term), the number of adolescents who consented and fully completed the questionnaire was 199, representing 77.4% of the target sample. This final sample size still provides sufficient power to detect meaningful patterns in knowledge, attitudes, and perceptions of sexual and reproductive health among Abuja secondary school students.

Eligibility criteria (Inclusion and Exclusion)
Adolescents aged 13 to 19 years who were currently enrolled in selected secondary schools in AMAC, FCT, were included in the study; those who did not consent to participate or for whom parental or guardian consent could not be obtained were excluded.

Data collection
Data were collected using a structured paper-based questionnaire adapted from previously validated SRH instruments [11-13]. The tool included sections on socio-demographic characteristics, knowledge, attitudes and perceptions of SRH. The questionnaire was adopted and modified from a previously published and validated SRH survey instrument. Face and content validity were established of two experts in adolescent health and public health. The experts independently reviewed the questionnaire for: clarity and appropriateness of language for the adolescent target population (age 13-19 years), relevance of items to the study objectives and local context, comprehensiveness in covering key SRH domains (knowledge, attitudes, perceptions, barriers), and cultural sensitivity and appropriateness for the Nigerian setting. Each expert provided written feedback, which was discussed in a consensus meeting. Items were modified based on expert recommendations some questions were reworded for clarity, others were removed due to redundancy or cultural inappropriateness, and additional items were included to address identified gaps. This process ensured that the instrument appeared to measure what it intended to measure (face validity) and adequately covered all relevant aspects of adolescent SRH (content validity). The instrument was pretested among 20 students (not included in the main study) to ensure clarity and reliability.

Knowledge was assessed through items on awareness, legal consent age, STI identification, fertility awareness, prevention methods, contraception purpose and methods, and HIV transmission myths. Correct answers were assigned 1 point; incorrect or “don’t know” answers received 0 points. For questions with multiple correct responses, each correct response earned one point. The total knowledge score (range 0-19) was categorized as: Poor knowledge (0-9) and Good knowledge (10-19). The initial plan to categorise into three levels (excellent, good, poor) was revised to a dichotomous classification (poor vs. good) to simplify analysis and improve statistical power for subgroup comparisons. Attitude was measured using Likert-scale items that assessed respondents’ evaluative judgments and predispositions toward SRH, including: (1) comfort discussing SRH with peers (reflecting social attitudes), (2) perceived importance of SRH education and services (reflecting value-based attitudes), and (3) views on contraceptive access and equity (reflecting policy attitudes). Perception was measured via items that assessed respondents’ subjective interpretations and understanding of their SRH experiences and environment, including: (1) adequacy of received education (reflecting perceived quality of instruction), (2) sources of SRH information (reflecting perceived accessibility), (3) comfort discussing SRH with parents (reflecting perceived family communication dynamics), and (4) views on media portrayals of SRH issues (reflecting perceived external messaging). While both domains included items about “comfort,” the attitude items focused on general disposition toward SRH discussions with peers, whereas perception items focused on the specific experience of family communication about SRH. For both scales, higher scores indicated more positive attitudes/perceptions, with reverse scoring for negatively worded items. Total attitude scores (range 0-13) were categorised as Negative/Neutral (0-8) and Positive (9-13). Total perception scores (range 0-30) were categorised as Negative/Neutral (0-20) and Positive (21-30).

Socioeconomic status (SES) was assessed using a composite index adapted from the Family Affluence Scale, incorporating: (1) parental car ownership (0 = no car, 1 = one car, 2 = multiple cars), (2) access to internet at home (0 = no, 1 = yes), (3) number of siblings (0 = 5 or more, 1 = 3-4, 2 = 1-2, 3 = none), and (4) type of school attended (0 = public, 1 = private). Scores were summed (range 0-8) and categorized as: Low SES (0-3 points), Medium SES (4-6 points), and High SES (7-8 points).

Data analysis
Quantitative data were tabulated appropriately to facilitate statistical analysis. Basic descriptive statistics such as frequency and percentages were calculated and used to summarise the data and analysis was done using SPSS version 25.0. Student t-test and ANOVA were used for comparing the mean differences in continuous outcome variables across two or more independent groups while correlation analysis was used to check for the strength and direction of the relationships between the continuous variables.

In addition, outcome variables (knowledge, attitude, and perception) were dichotomized as follows: knowledge (poor vs. good), attitude (negative/neutral vs. positive), and perception (negative/neutral vs. positive). Binary logistic regression analysis was performed to identify factors associated with good knowledge, positive attitude, and positive perception. Variables with p<0.20 in bivariate analysis were entered into multivariate logistic regression models. Adjusted odds ratios (aOR) with 95% confidence intervals were calculated, and statistical significance was set at p<0.05.

Data availability
The data supporting the findings of this study are available from the corresponding author upon reasonable request. The data are not publicly available due to privacy and ethical restrictions concerning sensitive information from minor participants.

Ethical considerations
The research protocol, including the consent process and all materials, was reviewed and approved by the National Health Research Ethics Committee of the Federal Capital Territory, Abuja (Approval: FHREC/2024/01/087).

Consent process: For participants younger than 18 years, parental or guardian consent was obtained through a two-step process: (1) Information sheets and consent forms were sent home with students for parents/guardians to review, which explained the study purpose, procedures, confidentiality measures, and the voluntary nature of participation; (2) Parents/guardians who agreed to their child’s participation signed the consent form and returned it via the student. On data collection day, these students provided written assent after having the study explained to them in age-appropriate language. Participants aged 18 years and above provided independent, written informed consent. All participants were informed that they could withdraw at any time without consequences. Participation was entirely voluntary, and no incentives were provided. All data were anonymised at entry to ensure confidentiality, given the sensitive nature of the topics.