I read a book in the late 80's early 90's. It was about a pandemic that kills all adults. Only children under 14-15 survive. The main charcter is a girl, she has a little brother and drives the car to her school. She sets up a safe place at the school and other kids try yo take over the school.  her and friends and kids she helps rescue all fight together against these attackers. They realize at some point they will have to start repopulating the earth.
That is all I remember. It may have been written in the 70's or early 80's.

Was it the Kindling by Jennifer Armstrong? I'm looking for the same book, the details sound the same but I don't know the title. Thanks.

Actually it's sounds like The Girl Who Owned A City, check it out on amazon.com.