These books have been getting popular at my school library across all grades (5-7), mostly girls. There are 7 books in the series. I have them listed as YA in my school. Titles center around athletic girls, some love interest. Titles include: “Pretty Tough”, “Playing with Boys,” “Head Games,” “Stealing Bases,” “Making Waves,” “Fifteen Love.” They have different authors. Liz Tigelaar and Nicole Shepherd are two. May be available only in paperback, I believe.