To be honest, your plot is bit unclear and seems to be just the regular lives of high school teenagers going through those phases. It's also a pretty over-used kind of setting. But what makes up for it is the new fresh air of the Apink you bring. New personalities. You can definitely improve though. Find plot twists and give the story a kind of goal to reach. Make the characters go through struggles to reach something they want/need. It won't be the greatest story if there is no complications. I f you can find the conflicts and work with them, then you can make a great story.