Oh, wow! For about 10 minutes last November -- or however long it takes to get on a rooftop and exclaim "I love simple solutions" -- the oh-wow crowd was wild about the Wisconsin legislature. It had found the answer to teen-age pregnancy: Stick it to the grandparents.

The legislature had passed the grandparents' liability law. If the teen-aged parents can't pay the bills for the baby -- and how many can? -- the law reaches into the deeper pockets of both sets of grandparents. They can pay weekly or monthly, but pay they must. The law demands that the grandparents of unmarried minors support their grandchildren until their children reach 18, marry or join the military. Parents who aren't up to teaching their kids the facts of life can themselves face the economic facts: Promiscuity costs.

With parts of the national media overplaying the grandparents' liability law, the simple answer, for once, appeared to be the right answer.

It was -- for 10 minutes. Then, reality weighing what it does, the roof fell in and the oh-wowing stopped. In the five months since the law's enactment, the complexities of teen pregnancies still bedevil Wisconsin. No case has come before the court to test the grandparents law. Lawyers are unsure how to go after the money because they are aware of the obvious defense: no rights, no liability. Grandparents taken to court by the government can argue that if they had no rights over whether the grandchild was given up for adoption -- or is to have day care, or other decisions -- then where is financial liability?

Three Madisonians familiar with the problems of teen pregnancy are Susan Heneman of the local Planned Parenthood office, Peg Scholtes of Connect, which is a program of volunteers who work with parents under 21, and Michele McCoy, a teen-age parent.

When I spent part of an afternoon with these women, a more important story emerged. The legislation that passed last November went well beyond the grandparents law. That was only one of 10 provisions in a comprehensive bill. The major part of the legislation establishes an $850,000 adolescent pregnancy prevention and services board. The 13-member group, which is to dispense funds to programs throughout the state, is regarded as a rarity because the law requires an equal balance of viewpoints on pregnancy prevention and services. That means an equal number of voting appointees who have what are called prochoice or prolife positions, with the chairman in a nonvoting position.

"There's the miracle in this bill," said Heneman: "Getting these two sides to sit down and work something out together." Much work still needs to be done. Groups that have been providing alternatives to abortion have often derided Planned Parenthood as proabortion zealots. The charge is false. Heneman explains that a difference exists between promoting abortion -- which neither she nor her organization does -- and providing information about its availability.

From the other side, groups like Planned Parenthood are beginning to understand that opposition to abortion is not automatically a right-wing venting. Many on the political left are arguing persuasively that abortion is another violent solution to a problem that can be solved short of ending a life.

The story worth watching in Wisconsin is whether the old rivalries and distrusts can be put aside. In face of the new half-million unmarried teen-aged mothers annually in a nation where 28-year-old grandmothers are becoming common, the Wisconsin law is cautious, if anything: Contraceptives cannot be sold in vending machines. Sex-education courses are to be designed by each of the state's 432 school districts, but the courses are not required to be taught. "Human Growth and Development" is the title, not sex-ed. Parents opposed to "human growth and development" have the option of withdrawing their children. The prevention and services board is not allowed to give grants for dispensing contraceptives in school health clinics.

Each of these parts of the legislation was debated out in hearings inevitably described as "stormy." The grandparents' provision, which received nearly all the national attention, is likely to have the smallest effect on the lives of the teen-agers. Put into the law with no previous study or debate, it was a gimmicky approach. It is due to sunset at the end of 1989.

The parts of the legislation that matters are the unshiny provisions that offer governmental services to children who can't get them elsewhere. Michele McCoy has asked: "Do we really want to go back to having the family, no matter how abusive, incapable or dysfunctional, be one's only resource for help?"

Anyone who answers yes to that question knows few American families, and fewer teen-agers.