Google Cast

Google Cast for Education is a free Chrome app that allows teachers and students to share their screens wirelessly from anywhere in the classroom. The app runs on the teacher’s computer, which is connected to the projector; students use Google Cast, which integrates seamlessly with Google Classroom, allowing the teacher to set student permissions and remain in full control at all times.
Here's a great tutorial showing you how to install the app and how, and why to use it with students.