The Association of British Pharmaceutical Industries has a useful feature on its web site showing the various options for students at different stages of education:
www.abpi.org.uk/medicine-discovery/academic-collaboration-education-skills/careers-in-the-pharmaceutical-industry/your-career/#5766b033
It's only one example, and there are obviously lots of other industries that employ people with chemistry/biology/maths backgrounds: food & drink, agricultural science, chemicals (huge range of options, including fuels, sustainable energy sources, etc.), environmental monitoring, health & safety, household products, personal care products, and on and on. And that's without even thinking about specialist areas of law, journalism, publishing, broadcasting, etc.
It's very difficult for school/college students to have an idea of how wide the range of options is, as you can't really guess what kinds of careers there are beyond what your family/friends' families, etc., do, or what you've seen on television/web/etc.
I've often tried to get groups of sixth-formers to produce lists of what they do & don't want out of a career before trying to identify specific pathways. For example, do they want to work regular hours (the idea of working 9-5 five days a week fills me with horror, but it's exactly what some people want), do they want to work in a team, do they want to work in one place all the time, do they want to work outdoors, do they want to work in a calm, quiet environment, do they want to be responsible for other people, do they want to work with the public (and with particular groups, e.g. children, elderly people, disabled people, people with significant personal problems), do they want to do lots of analysis, do they want to do something that requires prolonged concentration or something where they have to make decisions quickly, and so on. It's difficult to do because they tend to have a very narrow outlook imposed on them by the appalling education system of England, wales & Northern Ireland, but if you can get them to stop thinking about subjects and start thinking about roles, it can get you somewhere.