If you are in secondary school, then really students should be asking the teacher if they need help, not a fellow pupil.

In an ideal world, they should probably not be speaking to anyone, unless they are working in pairs in which case they should be talking to their partner only.

If people won't leave you alone, tell the class teacher to get it to stop, explain that it means you cannot get your own work done and it'll end.

I used to assist teach IT/Computing in secondary schools for a long time, so I know how it is in those classes.

NB. Personally, I would just answer the questions and enjoy helping people, you can get your own work done another time. When I was a young student it was the same for me - I loved answering questions, it is good public service and helps the staff out.