Has my school breached my privacy rights?

[Boquesha Sharice]

Long story short.. There were several people cheating on a French exam, and they want to find out who it is. So they went online to find our Twitter and Facebooks and any other social networking websites we use. And they have all been reading our tweets and sadly I never bothered with privacy settings on twitter. So I know that they are public and therefore anyone can read them BUT is my school wrong to try and find us online and stalk our twitters and facebook (I have strong privacy on there) because I believe that they have breached my right to privacy by doing so.. If we did it to them we would be in deep shit :/ Also I got into trouble for making my opinion and thoughts on what they did public surely I have the right to free speech and opinion as well but I think my school are forgetting this! SO ARE THEY IN THE WRONG? oh and I didn't cheat btw