Darcy (Molly Ringwald) and Stan (Randall Batinkof) are ambitious high school seniors with their whole lives ahead of them, and every detail of their future mapped out. Darcy is the editor of the school's newspaper and is looking forward to college where she will study journalism. Stan is headed to Caltech on a scholarship to become an architect.
After spending a weekend together, the couple discovers that Darcy is pregnant. The news throws them into a tailspin as they consider how a pregnancy affects their respective futures. When they announce the pregnancy to their parents, Darcy's mother (Miriam Flynn) and Stan's parents (Kenneth Mars and Conchata Ferrell) both feel that Darcy should either have an abortion or they should put the baby up for adoption.
Darcy chooses to have an abortion, but at the last minute changes her mind. Darcy and Stan decide to get married and keep the baby, much to the dismay of their parents. They marry and find an apartment. Darcy drops out of high school and chooses to pursue her GED, while Stan continues going to school and work part time to support them. Stan secretly turns down his scholarship to Caltech when he discovers that they do not provide married housing.
The baby is born the night of their high school prom, and the couple begins to really struggle trying to care for the baby and keep the bills paid. They are forced to move in with Darcy's mother and they quickly begin to grow apart. When Darcy finds out that Stan sacrificed his scholarship, she sets out to ensure that he can go to Caltech by breaking up with him and annulling their marriage.
It doesn't take long before both Stan and Darcy finally understand what really matters the most to them, and they realize they'd go to the ends of the earth for each other and their new family.