Society is more digitised than ever and there is an urgent need to train people in these sectors, where women are still under-represented. A quantitative descriptive, correlational and explanatory descriptive design was used to identify barriers, supports and gender gaps in Science, Technology, Engineering and Mathematics in Secondary Education by analysing the interest and perception of 1562 students and 432 teachers. Descriptive statistics, Chi-square and Lambda test and Crame's V or Phi test were performed together with a qualitative analysis. The results show that fewer female students want to pursue STEM studies, with girls preferring health and education professions and boys preferring engineering and computer science. Indeed, their motivation is different since we found correlations between being a girl and choosing STEM for helping people and society, while earning money is important for boys. Girls believe more necessary than boys to have qualities to study STEM and less often perceive themselves as intelligent and courageous. Our study revealed that families and teachers encourage more boys than girls towards STEM activities. Teachers believe that girls are influence by preconceived ideas, lack of STEM knowledge and lower self-esteem. Regarding gender equality, almost half state that no objectives are included in the curricula, 43.85% do not include it in subjects and only 30% received training. Consequently, female vocations need to be promoted by teaching how STEM solves real-life problems, fostering creativity, increasing self-confidence, promoting STEM activities and making female role models visible. Teachers should receive more gender training and promote gender-sensitive STEM education.