To see how fast Waconia High School is growing, just look at its walls.

Each year, seniors transform part of a white concrete hallway into a colorful tribute to their class, painted with purple school colors and handprints from every one of the 200-plus students.

Each year, the high school has 30 to 40 more students. Each year, the seniors move to a bigger wall.

They'll soon need not just a bigger wall, but a bigger school.

"I hope we're in a new building before we run out of wall space," Principal Mark Fredericksen said. "I don't see the growth stopping."

Waconia is among a dwindling minority of Minnesota school districts with surprising enrollment growth, despite a deflated housing market and tight financial times.

School district growth has been slowing for years in the state. Over the 2002-03 and 2003-04 school years, 150 districts grew by 3 percent or more, according to state data. This year, only 50 districts grew that much.

While Waconia school leaders embrace their anomaly status and relish the additional state aid that comes with new students, the trend also presents a unique challenge in difficult times: asking taxpayers for more money to expand.

Earlier this month, Waconia leaders announced a May referendum for money to purchase land for future schools. They admit it will be a tough sell during a still-weak economy that's compounded by one of the state's largest budget deficits ever.

In Elk River, schools also are nearing capacity. Yet the school district in the northwest metro area is holding off building and will reconfigure schools, add expansions or look more to online technology instead.

"People would love to have this problem and growth is good, until you get to the point where you have to stick a shovel in the ground," Elk River Superintendent Mark Bezek said. "Then all of a sudden it's, 'How are we going to pay for this?'"

Exurban growth

For years, suburbs such as Lakeville, Farmington and Prior Lake exploded with new developments. While those suburban booms have since dried up, young families are turning to exurban cities.

"We certainly aren't getting skunked, but it's enough," said John Hilgers, Waconia planning director.

Residents in Waconia, 40 minutes from Minneapolis, complained 15 years ago that the high school was built on the city's outskirts. Since then, housing and commercial developments have popped up; a Target store moved in a couple years ago.

And the school district has tried to keep up, moving preschool classes out of the elementary schools and the high school weight room into an empty classroom.

The 3,300-student district projects all of its schools will be at capacity by 2013 and continue to grow out to 2020; the 1,000-student high school alone is expected to reach 1,500 students by 2020.

About 50 homes are built annually in Waconia, down from about 200 a year, Hilgers said. But interest from builders isn't waning as young families move in, stimulating a slowed housing market.

"Waconia still has that rural feel to it even though we're a growing community," Hilgers said. "We're somewhat separated from the Twin Cities."

That's the case in places such as Elk River and Shakopee, once two of the fastest-growing school districts in the state. Growth is slower, but homes still pop up in places such as Otsego. The 13,000-student Elk River district is expanding by 200 students a year, or 1.5 percent.

Bezek expects another housing boom in three to five years as developers who bailed on projects return.

"I don't know too many districts that are growing by that many kids," he said. "It's that flight out from the metro. You don't see St. Paul, Minneapolis building new schools; they're closing schools."

Even in Lakeville, the school board recently approved closing a school. The housing boom in the early part of the decade has subsided.

"I predict you'll see in the next 10 years many more elementary schools closing in more districts because of enrollment drops," said Jim Skelly, a Lakeville school board member and district spokesman for Farmington, where enrollment has also flattened.

In Shakopee, the mid-decade housing boom bumped enrollment to about 6 percent every year. Now district growth is about 4 percent a year, or 250 to 300 new students. While it's projected to level off at 3 percent, that would still mean 2,000 more students in the next 10 years.

In Plymouth and Maple Grove, which is part of the Wayzata School District, 400 homes a year have been built in the past few years. Officials predict an additional 1,000 homes in the next four years. In Brooklyn Center, initiatives such as magnet schools have boosted enrollment 7 percent this year.

No new high schools?

The challenge for growing districts is how to fund new projects.

In the past 10 years, Elk River spent $200 million on new schools and renovations. Now, the district spends 50 percent of taxpayers' money on retiring its debt; the state average for school districts is 30 percent.

"That makes it hard for us to go out and raise more money," Bezek said. "We're getting to a point, how much more can the taxpayers give? The question looms out there: Should we ever build another high school in Minnesota?"

When four new high schools opened in the metro area in 2009, all in outer-ring suburbs, they were expected to be the last for quite a while.

Waconia may upset that assumption. School officials have quietly watched enrollment climb 5 percent each year, growing in students and success; the boys' basketball team's trip to the state tournament -- which ended Thursday with a 50-48 loss to Orono -- was its third in the past five years.

"We've intentionally flown below the radar, but we do realize how we're a unique district," Frederickson said. "People don't always know we're growing, even in the community."

Kelly Smith • 612-673-4141