5th High school ( upper classes) was founded in 1984 in Ilion, a suburb of Athens, Greece. It has been a school with a long-term educational contribution to the secondary education. Our school contacted an internal evaluation and we had recorded worsening of indicators at many levels. In summary, the problems that we had to face were students with special learning needs, the mixed-ability classes and school violence. The diverse groups of students are a new reality that teachers are called to cope with. The reasons are miscellaneous: students with special educational needs, students of various learning levels, of different socio-economical level, students from different cultural backgrounds. Most classes are characterized by great diversification, as far as the performance and educational corresponding are concerned during the educational process. It was necessary to reorganize teaching and learning in order to decrease the exclusion and to prevent discouraging certain students who need special treatment. Additionally, it must be recognized that during the last years and partly due to the economic crisis in Greece, the teenage students are involved more and more in violent incidents either between fellow students or students and teachers. As a result, the teachers of the school were having difficulty in controlling our students through old-school discipline methods. It was obvious that they are not adequate anymore. The in-service training in conflict resulution in the classroom is not only of great importance but the only way for the teacher to succeed in having a creative relationship with the students, as well. The action of this project is the answer to the major current problems that school was asked to face. The project included two mobilities: 1) Attendance of the course: “Special Needs Children”, by the Deputy Head teacher and two teachers. 2) Attendance of the course: “Classroom Conflict Management” by two teachers. These actions enabled school to re-engineer the teaching process, focusing on methods to manage classes of mixed ability students, helping kids with learning needs, reduce the percentage of prematurely leaving school students and those who quit studying at university, reduce bullying at school and help teenagers with psychological problems, give the chance to talented students to shine without being a problem that the classes are mixed-ability. Furthermore, the school improved teachers’ skills (educative, linguistic, cultural skills), adopted innovative teaching methods that will incite the creativity of both students and teachers, developed new approach in managing school which is consistent with European tendency, improved European profile through association with educational commissions and schools overseas, gained technical know-how to European programmes, network with schools in Europe.