Need children's book title circa 1960 - 1985, only remember plot
I'm trying to find a book I read when I was about 11 years old (1980s). I don't remember the title, but somewhat remember the plot. The world is plagued with a disease that kills everyone over the age of 15. The children are left to fend for themselves and band together in rival groups trying to survive. They hole up in old schools, raid grocery stores and attack each other. That's about all I remember. The cover is orange, I think. A book title or suggestions on where to locate this book would be great!
Thanks.