Jennifer Ball and her three-year-old, Zoe, walk through the paved lot next to their home, hopeful but anxious.

This lot is going to be the home of Zoe's future school, if all goes well – the first hyper-urban school Vancouver has ever built, four storeys high, shoehorned in next to the condo tower where the Balls live and across the street from the arena that is home to Canucks games.

The school is due to open in 2015, and will be cantilevered over a nearby park to get more space to accommodate the 200 extra students it is expecting beyond the original estimate of 300 – an indication of how much the downtown family population has grown. The city approved the unusual architectural feature this week, and a community open house was held a week ago.

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"I was so excited as soon as I see the posting in our elevator, oh my God," says Ms. Ball, a pre-op assistant at Vancouver General Hospital, where her husband, Jacob, also works as a nurse. "It would be perfect for us to have that convenient school for her."

She's a little worried, because if it is over-subscribed, admission will be determined by a lottery.

The Balls and hundreds of other families are choosing to stay in downtown Vancouver after they have children instead of fleeing to the suburbs as previous generations have.

Ms. Ball said she cannot imagine moving to a place like Surrey and commuting a couple of hours each day. The Balls – she is from Manila, her husband is from Petawawa, Ont. – do not own a car and have no plans to get one. The most they want to expand, for the next baby, is moving from their two-bedroom condo to a three-bedroom in the same building or nearby.

Her time with her daughter is important. Today, she and Zoe are taking an after-work walk near the condo, picking blackberries that grow wild in the park, and watching out for needles that drug users occasionally leave in the bushes. Then the two will head to Costco for groceries.

The life the Balls are choosing is a result of years of city efforts. Planners have insisted that a quarter of all new developments downtown be two bedrooms or larger to accommodate families, and that they have child-friendly amenities.

It's been an unqualified success.

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According to the 2011 census, the number of children under five doubled in the previous five years. There were 1,840 children counted downtown in the zero to four category, compared to 875 in the five to nine bracket – an unmistakable baby boom.

That makes the downtown one of the city's most heavily toddler-populated neighbourhoods, in the same league with single-family areas in the East side, and a stark contrast to the West side, which is seeing a decline in child numbers.

But for the Vancouver School Board, it has meant a new approach to school building.

"This particular school is going to be all about flexibility," says Kelly Isford-Saxon, the board's project manager. "And it is different. It's going up four floors. That was one of the hard things, to think about how to create a community going up, not going out."

The last time the board built a downtown school to accommodate the baby boom, Elsie Roy Elementary School in nearby Yaletown, it used the traditional architecture. It is two storeys high, although the school did capitalize on having the park next door for school activities.

This is the first one built on such a small site – but not the last.

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"What we do here is going to signal what happens in the rest of the downtown core and other areas that are densifying," Ms. Isford-Saxon said. With City of Vancouver and University of B.C. planners both figuring out where to layer in new density to their territories, the board envisions similar schools in many other places – another elementary and possibly a high school downtown, schools at the university, along Kingsway, at the Olympic Village, in the development along the Fraser River in the city's far southeast corner, and more.

The school board sent five people to New York City, where they combed through nine different schools from P.S. 246 in Manhattan's Battery Place to P.S. 210 in Harlem, as well as the Bronx and Brooklyn, to see what works (and does not) for ultra-urban schools.

Things school planners have to think about: noise (from elsewhere and from their students); how to move children around and keep them connected vertically, rather than horizontally; how to mesh with the neighbourhood outside the doors.

"It's a question of how do you manage that deliberate balance of inserting a school into an existing neighbourhood," Ms. Isford-Saxon says.

That research has led to the idea of a rooftop deck on the school for quieter outdoor activities, while the park will be the area for running around and shrieking kinds of activities, as well as having ground-floor rooms available for after-school care and community use.

A few people around the planned school have scoffed at the idea that families will stay downtown.

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Charles Wong, who also lives in the Firenze Tower next to the site, is not one of them.

"I actually like it. It provides for people nearby to have a school," says Mr. Wong, a retiree who spent his working years in West Vancouver. He said his floor alone has one family with four children and another with an eight-year-old.

The one question school officials have not answered: What will happen when this new baby boom reaches high-school age?

"Ten years ago, people didn't expect families. But they came," school board chair Patti Bacchus said. "Now we don't know, do people move away when their kids become teenagers? That's kind of the next chapter we haven't written yet about this whole moving-downtown thing."