What did you apply for? I thought they reply later in the yer.
I'm sure it'll be fine, the summer school is there to give people a new experience anyways so I doubt the universities will expect you to know everything. People will just have finished Year 12 anyway so there's still a year left of content.
I guess they still want you to be passionate about your subject stream and know what it entails. No good applying for a subject that you have no interest in x