You need to show that you havent just studied the whole way through school without developing any other interests. extra curricular interests develop many of your skill sets. Teamwork, dedication, leadership, self discipline, communication, providing excellence, etc These employers find attractive because not only do they want people who can do the job but people who can work in teams and ‘get on’ with the people they work with etc. Part of that can just be having something else to talk about other than work.
Basically you should write as much as you can about your other interests and what skills you have developed out of these that you could apply to the workplace.
So team sports will help develop, communication, leadership and team work. Whilst Individual sports can develop determination, self discipline and providing excellence skills. Same with music, in a band/orchestra or solo. Other interests can be drama etc. Or independent travel which can develop independence, communication, as well as cutural understanding and broad experience.
You could put volunteer experience down, as this shows dedication, commitment, self discipline etc.
There lots you can talk about - just need to think what you do or have done when not studying. If its hosting social events/organising balls then this is useful as well as can show planning/organisational skills as well as committment etc.
Ideally all they want to see is that you recognise that having a social side is important and spend some of your life having fun. Whilst recognising that the skills from this ‘social side’ helps to make you a better potential employee for the skills that you gain from doing those things.
Lot of people bleat on about “filling their cv’s” and whilst it is important to be able to show you have interests, you can always explain that you do have interests such as … and … but dont find much time to get involved as much as you would like because of … part time job/caring for family/travelling back and forth for study/etc but then describe skills you gain from doing those things you spend doing instead of having extra curricular activities.
Hope this helps a bit…