The declaration of the Decade of Education for Sustainable Development (DESD, 2005-2014) explicitly highlights the need to incorporate sustainability issues into the curriculum. In this context, Education for Sustainable Development (ESD) is seen as essential to promote changes in individual decisions and behaviour and to demand actions by the competent authorities in the educational, scientific-technical, political-economic, and social spheres. In addition to responding to international education requests, it is important to consider the interests and needs of students to make ESD a reality. Education is intended to contribute to the development of the right of the upcoming younger generations to take active roles in a society that requires informed citizenship committed to the development and implementation of actions to overcome the socio-environmental crisis. In this context, an analysis of students' current conceptions of this problem, which is increasingly worsening, was considered relevant. Accordingly, and considering previous research, this study poses the following hypothesis: Secondary school students are concerned about Sustainability issues in general and about accelerated Climate Change in particular but lack the necessary basic knowledge and the appropriate resources to deal with them. To test this hypothesis, during the 2019-2020 academic year, a sample of more than 500 Secondary school students from different educational centres in Spain were asked about their concerns regarding socio-environmental issues, analysing specifically those related to Sustainability and Climate Change, as well as their knowledge regarding such issues. Students completed an extensive questionnaire organised in seven blocks and aimed at encouraging reflection on Sustainability, addressing their alternative conceptions and exploring their interests and motivations. This study addresses the answer to some of these questions.The declaration of the Decade of Education for Sustainable Development (DESD, 2005-2014) explicitly highlights the need to incorporate sustainability issues into the curriculum. In this context, Education for Sustainable Development (ESD) is seen as essential to promote changes in individual decisions and behaviour and to demand actions by the competent authorities in the educational, scientific-technical, political-economic, and social spheres. In addition to responding to international education requests, it is important to consider the interests and needs of students to make ESD a reality. Education is intended to contribute to the development of the right of the upcoming younger generations to take active roles in a society that requires informed citizenship committed to the development and implementation of actions to overcome the socio-environmental crisis. In this context, an analysis of students' current conceptions of this problem, which is increasingly worsening, was considered relevant. Accordingly, and considering previous research, this study poses the following hypothesis: Secondary school students are concerned about Sustainability issues in general and about accelerated Climate Change in particular but lack the necessary basic knowledge and the appropriate resources to deal with them. To test this hypothesis, during the 2019-2020 academic year, a sample of more than 500 Secondary school students from different educational centres in Spain were asked about their concerns regarding socio-environmental issues, analysing specifically those related to Sustainability and Climate Change, as well as their knowledge regarding such issues. Students completed an extensive questionnaire organised in seven blocks and aimed at encouraging reflection on Sustainability, addressing their alternative conceptions and exploring their interests and motivations. This study addresses the answer to some of these questions.