Two of my DC did their first work experience with local charities. DS worked with adults with learning difficulties and now has part time paid career job while at uni. DD was at women's aid for a week and what an incredible eye opening week that was for her.
Their friends were all over the place - cafes, hairdressers, local government, nurseries, schools, universities, the nearby observatory, golf club, advertising agencies, one was at Kwik fit.
It really doesn't need to be career based at 15, just some experience of going to work every day.