Mathematics education is a very important factor influencing individual's life chances. People with unsatisfactory mathematics skills often meet severe limitations in their choices at the job market in technology-rich society. Therefore mathematics school education for all citizens is recognized as the field to be promoted across Europe. The needs of diverse population of pupils in secondary schools are addressed by actions that aim to narrow the observed gaps in mathematics skills and to reduce the share of underachievement. Despite the obvious employment possibilities that require mathematical knowledge and skills, at the secondary school level pupils show low interest, widely spread negative attitudes and low achievements in mathematical literacy. Even more, as a consequence of lacking knowledge in mathematics and science, in higher education students face problems concerning academic success, which then lead to a high rate of a dropout in higher education.Research confirms that most students are not able to acquire basic skills without meeting situations in which these skills are to be used and which are perceived as meaningful (practically, intellectually) by the students. Therefore, the MERIA project will focus on educational paradigm of problem-based learning by making mathematics relevant and interesting to students, and in particular on development of teachers’ competencies to establish appropriate “inquiry situations”. Through resolving these situations, students acquire and apply basic mathematical skills. Development of student-centered methodology will be based on the two well established strategies that are solidly rooted in research (the Realistic Mathematics Education and the Theory of Didactical Situations) in the partner countries. The results of the project activities ensure a repository of good practices as a new curriculum material that can be transferable together with methodological framework for implementation and evaluation of mathematics education across Europe. Didactic materials designed during project will help teachers create classroom situations that promote deep learning approach, power of mathematical modelling and abstract thinking. All materials will be published with Creative Commons License and will populate national digital repositories (in Croatia E-school digital repository).The undergoing curriculum reform in Croatia is an additional opportunity for the project to re-conceptualize and implement new ideas in mathematics education. In doing so, its impact in Croatia will be huge as it will guide numerous teachers' transition to new methods of teaching and learning. Above that, the main value of the project lies in the creation of a framework for relevant problem-based mathematics education using a systematic approach and design of reference materials for the repository that will continue to be developed by partner institutions after the project ends. MERIA project intends to address the underachievement but also “overlooked middle” in mathematics by taking into account actual needs of stakeholders in the educational systems within the partnership countries. As the project strives for inclusiveness, indirect stakeholders for the projects’ results are all teachers and students participating in secondary education. The project will support the curriculum in participating countries by enhancing teacher participation and offering teacher training. The support for teachers is also offered for design of their own lecture materials, thus highlighting their “21st century” competences (European Reference Framework) such as creativity and critical thinking. It is estimated that 180 teachers will be actively involved in the projects activity, either completing the workshop program or attending the international teachers’ conference. Direct users of project actions will be chosen based on their role in the local educational bodies and thus we will ensure that reaching more teachers through follow-up activities will be more effective. The project will enhance the collaboration between educational and research institutions and it will increase the level of exchange of experiences and good practices among high-schools across Europe. Thus the project MERIA will be a solid starting point for further educational actions of the partnering institutions supporting teachers’ professional development, addressing under-achievement in mathematics, promoting key competences for lifelong learning and it will have a significant role in strengthening the impact of education on youth employment.