Zoom is a video conferencing app accessible through any smart device — iPad, Chromebook, phone, etc. — that allows you to host sessions with up to 100 participants, completely free. If you’re planning to break students into small groups or record your sessions to repost for students who missed the call, Zoom is a good choice.
Google Hangouts Meet
Google Hangouts Meet is a great online tool for teachers that allows up to 100 participants in a video call. As a host, you have the option to mute and share screens with your students. Google Meet is included with G Suite and G Suite for Education.