Availability of attachment relations and safe school environment are associated with subjective well-being in 15-year-olds – with girls reporting less well-being and less equality

•An absence of feeling secure in the school environment and a lack of close and trusting relationships were linked to worse adolescent subjective well-being regardless of gender.•Girls and boys with better well-being reported optimal attachment and secure close relationships, as well as less insecurity due to behaviours of people from previous relationships and low feelings of insecurity in the school environment.•Girls reported worse subjective well-being, experienced more harassment in school and on social media, and experienced receiving fewer benefits than boys.