Here are some apps that provide free and secure way of online teaching.
1. Google Hangout Meet
Download it from here. First of all this app is made by Google Inc. So it is fast and secure with trust of Google.It is available for free to its users, is one of the best apps that is available for online teachers and helps them to conduct video conference and recording the same in Youtube. Talking to your students via videos even during your working hours is all possible with Google Hangout on your smartphone.
Classroom is a free service for schools, non-profit organisations and anyone with a personal Google account. Classroom makes it easy for learners and instructors to connect with one another – inside and outside of schools. Classroom saves time and paper, and makes it easy to create classes, distribute assignments, communicate and stay organised.