Wrong! Teachers must work far more hours than those when students are in school. Besides meetings, parent conferences, and attending performances and events outside of school hours teachers must do a lot of other time consuming things.
Preparing lesson plans takes quite a bit of time, especially if the curriculum has changed or the teacher is working at a different school or teaching a different grade level than he or she is used to. And there's lots more involved than simply following a book. Good teachers adapt the lesson plans to the specific needs of their classes. and with dozens of students in each class that isn't easy.
Teachers need to set up and arrange their classrooms and keep bulletin boards and displays relevant to the current topics their classes are studying. Those who work with younger kids might need to do those time-consuming things more often than those who teach teens.
Of course High School teachers must spend more time reading and grading papers and tests and recording the grades than those who work with young children do, but all teachers spend many hours a week doing those things. Ten hour work days aren't unusual.
Teachers must already have at least four years of college and a year or more of post graduate studies to qualify for the profession, and they get paid less than people in other professions requiring that much education.
But that's only the beginning. Often when schools are closed and students have vacation time the teachers are attending training sessions, learning to use new curriculum, etc. and lots of them take more graduate level college courses during the summer to learn how to do their jobs even better. Of course they must pay for those classes themselves.
One teacher influences hundreds of students who may go on to influence hundreds, or even thousands, of other people so teaching is one of the most important jobs in the world.