***Professional CLIL with a focus on science at grammar school Leibnitz, Austria*** Being one of the founding schools of a hands-on project-oriented approach to science instruction in one of the largest grammar schools in the province of Styria we feel it imperative to make an increasingly cross-linked European business world our key issue in the second year of our two classes taught in English as a medium of commmunication. In order to guarantee long lasting productive and receptive language skills (as described by CEF) , we aim at continuing two CLIL-classes from age 10 to age 14 onwards (about 60 participants out of about 250 new students) in every year, using English as a working language in as many science content lessons as possible providing an authentic and motivating learning situation, which later French, Italian and Spanish teachers can build a multilingual focus on. Therefore, six of our colleagues developed their competencies language-level wise (Europass) as well as methodology- wise. In addition to their main targets of general language development and advanced CLIL techniques with a strong focus on science, online-cooperation via eTwinning was increased. Starting off these special classes with native-speaker-support, the intensity of CLIL contents was increased continuously, enhancing the programme with special project days which required our students to immerse in authentic situations, present subject contents and cooperate within their class, with their teachers as well as with European partners. The programme was monitored as part of our school's quality development initiative.