No one wants to attend my society at school

Advertise? You need to put up leaflets and flyers around the uni. Maybe even get your lecturer to promote your society too.

I think the OP is still at school; OP, why don't you ask your guidance teachers to help? So for example, perhaps ask them, to tell those students who they know want to study medicine, about your society, or perhaps ask one of the science teachers?

Like someone above said you need to advertise your society. Try making a facebook page if you have facebook. Maybe people are reluctant because they don't know what to expect. Tell people what you plan on doing/discussing in the meetings and invite people to share their ideas on how to improve the society and what they would like to do. You could maybe ask your school if they could organise trips to universities to have a look at their facilities and get work in their labs maybe people would like that and join your society.

I told them what to expect and I also said that they should come and try and see if they like it and if they don't they can walk out.I tell people to spread the word but I don't think they are and when I asked for it to be mentioned in assembly they teacher said no.I have no printer ink unfortunately it is advertised on the school tv.

Well your teachers are being stupid then they should be encouraging you. Ask them if you could get up at the next assembly and talk about it yourself? When do you have the meetings? If you have them during lunch or after school then people may be too busy or reluctant to come. Try having them during morning break or free periods if you have any. How long has it been since you started and how many members do you have? Most societies start of small anyway just carry on having meetings with whoever decides to show up and if they like it then they might tell their friends about it and your society will grow.

EDIT: Ask people why they don't want to come. If a lot of them say they don't have the time etc then you could consider having an online chat group on WhatsApp or facebook it would be a lot easier for people to manage then and it would be easier to communicate so if somebody wants to ask a question all they have to do is put it in the group chat.

Our lunch is only 30 minutes and our break is 10 minutes so too short to do anything if I am honest.Free periods do not work as we would not be allowed as well as I need to be supervised and everyone has different frees.

What age are you?

Why do you need to supervised?

What about having it after school?

16,I need to be supervised because my head of sixth form says so and I will be doing it after school.

Who is supervising it? Ask them to help with recruiting.

However, if you already spoken to likely fellow medics and they aren't that interested it's really up to them. You can't force people to be in your society...

People claim they want to do medicine but they don't seem to really show it if I am honest.I had to switch the supervisor last minute and I asked them to promote it but it seems unlikely that they did.