This research used a multi-informant approach and Bronfenbrenner’s bio-ecological model (2005) as a lens to gather perspectives and experiences of autistic girls, alongside their parents, about their school experience and how this interacts with their pathways to diagnosis. There is limited academic research about these topics from the first-hand perspectives of the girls themselves. Semi-structured interviews and a personal construct psychology (PCP) tool (‘the ideal/non-ideal school’) were used to gather the experiences of eight girls and five of their parents, which allowed triangulation of data. A participatory and inclusive approach was taken throughout the research process to support the girls’ participation. Data were analysed using reflexive thematic analysis and four themes were identified: (1) the environment plays a huge role in how I can learn; (2) people aren’t predictable – navigating school relationships; (3) the journey to diagnosis – it didn’t come from school and (4) adapting to my new identity. These themes told the story of the girls’ journeys through school and how many environmental and relational elements had a huge impact on how they learnt and on their level of acceptance and comfort within school. Furthermore, their eventual diagnoses came not because of support from school or educational psychologist (EP) involvement but following intervention from external agencies. Being diagnosed during their adolescent years had an impact on the girls’ rapidly deteriorating mental health during the later years of secondary school; a time when additional support could have been helpful in ensuring the girls adapted to their new identities.