Why going to lesson is important:
Turning up to lesson and participating is extremely important. Without the face to face teaching offered in a lesson, learning English or any subject can be very difficult. What's more, turning up to things even when you don't want to is good for developing self-discipline. What you don't turn up to can never be of benefit to you. It also means that you are learning at the same rate as your classmates.
It is also important for keeping on good terms with future employers. When you get a job, not turning up or arriving late is unacceptable. You will quickly find yourself without a job if this is what you plan on doing.