Music is a source of joy and an important means of expression for many KLAS students. KLAS provides students with opportunities in which they can dedicate themselves to their favourite kind of music and develop as musicians.

More than half of all KLAS students are involved in voluntary music-related activities. They contribute to a variety of musical events including concerts inside and outside school, and enter prominent music festivals in Europe, all in an effort to develop their skills.

Every April, after five months of rehearsals, KLAS students put on an English musical for the community of Leysin. Approximately two-thirds of the student body are involved in the event. Student involvement is not restricted to acting. They also oversee music, choreography, costumes, hair styling, make-up, sound and lighting, and help to build sets and props. Many local people look forward to the annual production and marvel at all the work that is done on a voluntary basis after school.

Students can choose to take the Music Theory and Practical Examinations of the ABRSM, an organisation accredited by several music universities in the UK with histories stretching back to the late 19th century.

About 500 students from 15 international schools take part in this event. Students showcase their musical abilities, and specialists in each category evaluate and advise them.

Talented students come from around the world to play together in an orchestra or sing together in a choir. Over 800 students audition, and 250 students are selected every year, including some KLAS students.

Formal after-class sports activities are an important part of school life. All students participate in at least two supervised afternoon activities each week, and each activity meets at least one afternoon per week. Students choose among a variety of sport or recreational activities, depending on their own interests and faculty talent.

Leysin, one of the major ski resorts of western Switzerland, provides excellent sporting opportunities during the winter months. All students take part in skiing or snowboarding activities two full afternoons per week and are instructed by the Swiss Ski School. The KLAS ski team competes internationally against other schools and youth organizations.

Students actively participate in sports competitions sponsored by the SGIS, a group composed of 40 international schools within Switzerland, and ADISR, a group of schools from the French speaking region of Switzerland.

These activities originate from voluntary activities of the students, and are operated mainly by students under the approval of the student council and supervised by faculty. They deepen the interaction with other international and Swiss schools through sporting events such as football, volleyball, basketball, tennis, and mountain biking, all amid the beautiful natural surroundings of Leysin, Switzerland.

The Aigle-Leysin Marathon, one of the events held in conjunction with the Swiss National Day on August 1, is a gruelling, mountainous half-marathon in which participants run from Aigle (at an altitude of 400m) to the summit of La Berneuse (2,000m), and back down to Leysin (1,400m) on a 13.1 mile (21km) course. Well-trained KLAS students take part in this event every year.