There are several mirror/casting apps, but it does depand on what type of device you have and which iOS at time. here are some suggestions to get you started:
Reflector, AirServer, Chromecast to reflect/mirror your preso and have students mirror their's.
Nearpod and Docerio allows for presentaion of your preso, share with students and annotation.
Lastly, here is a collection of resources here with more detailed explanations: Ipad Educators
Best of luck to you!
One other option to Naomi's great list: Actiontec has an education-specific wireless display adaptor, the Screenbeam that works well with Windows 8 devices and is password-protected so only the teacher can share her screen (and students can't hijack it).