Just this past year in Columbia Heights, something very important has changed.

"After years and years of declining enrollment," said Bill Holmgren, finance director for the city's schools, "we had more kids last June than we had the year before." And the trend is expected to continue -- to the point, he said, where "we're going to have to add onto our elementary schools or bring in portables or something."

But that, he said, is a delicious problem to have, compared with the alternative. "I'm just happy it's not falling. It's hard to go to your union and say we need to cut more people. I don't want to do that anymore."

Census 2010 numbers being released Thursday show that parts of the Twin Cities area that have been aging for decades are suddenly filling with kids. And other parts of big suburbs on all sides of the metro area, long associated with families are losing those kids by the thousands as parents age and kids grow up and move away.

"I moved into Lakeville 25 years ago, when there didn't appear to be many senior households at all," said John Carpenter, whose firm, Excensus, tracks demographic trends. "That has really changed. No one would have ever thought back then that Lakeville would already be closing schools."

A number of factors are contributing to the shift in the balance of aging between newer and older suburbs and cities, Carpenter and other experts say.

One is the spike in housing foreclosures, which has pushed many young families out of the Scott Counties of the world and back into the inner metro area in quest of affordable places to live, often to rent instead of own.

Another is the movement of immigrant families, as they establish themselves, into first-ring suburbs, often bringing with them higher numbers of kids per household than native-born Americans. "We're now more diverse than Minneapolis," Holmgren noted.

To be sure, the outermost and newest suburban and exurban cities in a ring from Rogers to Victoria to Farmington are still the youngest cities in the seven-county metro, expressed in terms of kids school-age and younger. And inner-ring suburbs have the greatest share of seniors.

But surprising things are happening within that standard picture.

School officials in Edina have been struck by the numbers of youngsters still flowing into the schools, despite a notably aging population, and have wondered whether it's because the decline in home values has made the city more affordable for young families. Indeed the census found a 751-person increase in the under-18 population of Edina. That's more than Columbia Heights, which grew by 614 children but registered a percentage gain that is more than twice Edina's.

Big losses on the other end struck Minneapolis and St. Paul, which declined by 6,000 to 7,000 kids each, but also a range of suburbs. Eagan dropped by 2,700 kids to register the biggest suburban fall, while Coon Rapids, on the other side of the metro area, declined by 2,635 people age 18 and younger.

Others losing more than 1,000 kids since the year 2000 -- a loss that affects a range of community institutions, from water parks to Sunday schools -- include Minnetonka, Shoreview, Burnsville, Champlin, Bloomington, Oakdale and Apple Valley, with Plymouth just short of that figure, losing 994.

David Peterson • 952-882-9023