The yellow school bus pulled into City Hall Plaza yesterday and people whipped out their camera cell phones and started shooting pictures.

This was no ordinary school bus. This was a bus named Topsy-Turvy.

Topsy, as she is known by those close to her, is really a bus-and-a-half, with the upside-down half of a second school bus, its wheels pointed skyward, welded atop the roof of the first bus.

Being camped out outside Philadelphia City Hall was a fitting setting for the upside-down bus.

For Topsy is a political machine all on her own.

Designed by Ben Cohen, co-founder of Ben and Jerry's Ice Cream, the bus was created to make Cohen's point that the federal government has its spending priorities upside down, with too much spending for obsolete defense weapons and not enough for education and health care.

Cohen heads a political-activism project called the Priorities Campaign. The bus will be used to follow the presidential-primary campaigns.

"Our nation's spending priorities allow crumbling schools, millions of children with no health coverage, dependence on Middle East oil and deficits as far as you can see," Cohen said in a statement.

On the plaza yesterday, the bus was being used to draw attention to the lack of funding for the Philadelphia School District.

There were signs attached to the front of the bus that read: "Invest in Kids."

And stalwart public-education advocates Shelly Yanoff, executive director for Philadelphia Citizens for Children and Youth, and Sheila Simmons, PCCY'S education coordinator, led a small demonstration of people who chanted along to drum-beating: "More Money for Schools!"

Noting that the school district has a $37 million deficit this year and is projecting a deficit of from $150 million to $180 million next year, Simmons said both the city and the state need to contribute more to public schools.

"Ongoing budget cuts threaten to undo years of pace-setting academic progress and send the Philadelphia system moving backwards," she said.

Tom Kennedy, the San Francisco-based artist who created the bus, along with about 10 fellow artists, said the bus has been making a number of stops. He and artist Haideen Anderson are driving across country to deliver it to Cohen in New Hampshire.

On Sunday, Topsy attended the Code Pink Mother's Day protest against the Iraq war in Washington, D.C.

Yesterday, Code Pink activist Deborah Zubow took part in the protest at City Hall.

"It will be a great day," she said, "when our schools have all the money they need and the Air Force has to hold a bake sale to buy a bomber." *