Downtown's population under age 5 is among the central city's fastest-growing demographic groups, the Downtown Seattle Association says.

But when those kids reach school age, they and their parents leave. That needs to change, Downtown Seattle Association (DSA) President and CEO Kate Joncas said in her annual "State of Downtown" address Wednesday.

The advocacy group is working on several initiatives to keep families with children downtown, she said, including establishing outdoor play space and a downtown elementary school.

Downtown loses kids when they hit school age at a faster rate than other city neighborhoods, according to a DSA analysis of census data.

In 2000 there were 776 kids age 4 and under living in greater downtown, which stretches from Lower Queen Anne to Sodo. In 2010, however, there were just 394 children ages 10 to 14.

That suggests about half of 2000's toddlers and preschoolers weren't living downtown 10 years later, the DSA says. Citywide, the decline was just 14 percent.

In an interview after her address, Joncas said the association is working with Seattle Parks and Recreation to create outdoor play space in the downtown core. Something could happen soon, she said.

Parks spokeswoman Dewey Potter said the department hopes to find money to establish a pilot play area by summer. Westlake Park and McGraw Square, at Fifth Avenue and Stewart Street, are under consideration as short-term options, according to the DSA.

Joncas also said the association has begun talking with Seattle Public Schools about an elementary school in greater downtown. The city Department of Planning and Development also is involved, she said, and several information-technology and life-sciences employers in South Lake Union and the Denny Triangle have expressed interest in becoming partners in the effort.

Downtown now is served by elementary schools in Queen Anne, Capitol Hill and the Central District.

Seattle Public Schools spokeswoman Lesley Rogers said there are no plans for a downtown elementary anytime soon. Other neighborhoods have more need for additional capacity, she said.

Joncas' address was part of the association's annual State of Downtown Economic Forum. Nordstrom President Blake Nordstrom was the featured speaker.

Eric Pryne: 206-464-2231