Why is summer school a thing?

Like I know some people struggle and have a lot on their plate and it's good that they have it. But at my school every one has to take summer school.<br><br>With the way my schedule works I have to do the summer school and then still do the class in the upcoming year. When I don't have to do it. And I'm not the only one. Why isn't there an option to do the summer school and be done with the class.