The main aim of the project "The linguistic development of teachers" was to improve the linguistic competences of the project participants, teachers who don't teach English language. In the training provided by Executive Training Institute Malta (ETI), three teachers took part: a maths teacher, a science teacher and a teacher-headmaster. The improvement of language skills of teachers was to increase the chances of school to participate in interdisciplinary international projects. The project aims were clear and precise: - improving language skills and the educational level of teachers, - getting to know the diverse systems of education and teaching methods, - realizing international projects with the active participation of teachers of all subjects, not only language teachers, - preparing teachers for effective work within EU community with the usage of the lifelong learning attitude, - broadening the educational offer by implementing interdisciplinary projects in English. Owing to the training, the teachers improved their linguistic competences, both in speaking and writing. The usage of English during classes, in everyday situations on the English-speaking Malta, in the contact with other teachers from all over the world present during the course, helped to overcome the language barrier which was an obstacle for them to participate in international projects. Apart from increasing linguistic competencies, the teaching staff raised their motivation to learn foreign languages, also thanks to didactic materials obtained during the course. The training in the international environment gave them possibility to share their own experiences with other teachers from different countries. They got to know the new teaching methods, diverse systems of education, learnt about history, culture and customs of different nations. The participation of the school in the project strengthened the quality of the European teaching, thus promoted the school in the region and abroad. The course was led with the usage of the newest IT methods, which resulted in the development of IT skills. The classes were conducted with the application of activating and motivating methods - the teachers could become familiar with new techniques, which are not so popular on science and maths lessons, as: role-play, mini-lecture, brainstorming, discussion, group work, pair and individual work, project method. The school in Malta implements numerous international CLIL projects; owing to its wide experience in this field, the school education staff was able to get to know more about this method and obtain the access to interesting tips and materials connected with this method. The development of the language skills took place not only during the mobility, but also in the course of the whole project. The teachers actively took part in establishing the partnership with seven European secondary schools, which resulted in the elaboration of the project entitled "Beyond Limits" in Erasmus+ Key Action 2. All the works on the project were conducted in English language. The school has also started to work on the international project with a twin city - Ghent. Thanks to the cooperation within a one-year project, responsibilities for particular tasks, the teachers had the chance to work in groups, in the frame of different subject teams. The common school projects were discussed, the interdisciplinary materials were prepared, for example: worksheets and lesson plans, Polish-English Mathematics dictionary, the collection of mathematical problems, which can be used during classes. To raise the competencies not only of teachers but also of students, with the usage of activating methods - project method, numerous presentations and films in English were prepared - with the application of CLIL elements including interdisciplinary content, with specialist vocabulary, English-Polish mini dictionaries joining biology (ecology, environmental protection, fauna and flora of the Baltic Sea), geography (landforms, elements of tourism connected with coastal area on which the school is situated), maths and foreign languages. Thanks to the mobility, the project participants were able to grade not only the substantive side but also the linguistic aspect of these materials. In a school library there is a brochure containing all didactic materials received during the international training, which can be used by every person interested in developing linguistic competencies. There is a special section on the school website informing about the realization of the project, containing all results and products created during the project, which are widespread and available on the Internet, YouTube or SlideShare.