Like in many children's bedrooms, a model of the solar system hangs on the wall, and backpacks and stuffed animals line the shelves. But this room - 10 feet by 10 feet - isn't just a child's room. It's the entire home of four children, their parents and two dogs.

Laura Chinas, 42, and her husband sleep on the floor, and her kids, ages 4 to 11, sleep crammed on the lower part of a bunk bed. The family's belongings pack the top bunk. They have no bathroom or kitchen of their own. Mice and bedbugs also call the tiny room home.

And the rent for this worn, rodent-infested home that's not much bigger than a parking space? A thousand dollars a month.

The tech-fueled economic boom has hit 16th and Mission streets in a big way, bringing with it Google buses, expensive condos and high-priced restaurants and boutiques. But just a few properties down from the famed intersection is the dubiously named Grand Southern Hotel, a single room occupancy hotel with 60 units. Many of them house families, and 22 children live inside - the most of any SRO in the Mission.

Increasingly, this is what life is like for children on the lowest economic rungs in one of the richest cities in the world. Fifteen percent of children in the city live in poverty, up from 10.7 percent in 2008, according to census figures.

There are hundreds of SRO hotels, in which residents live in a room and share communal bathrooms and kitchens, in San Francisco, mostly concentrated in the Mission, South of Market, Tenderloin and Chinatown. Many are run by nonprofits, while others, like the Grand Southern, are privately run and are for-profit. Some SRO residents receive government assistance, but others don't.

Numbers likely rising

The San Francisco Human Services Agency in 2009 found that roughly 1,200 children live in SRO hotels in San Francisco. There has been no formal census of SRO residents since then, but those who work in the field believe the number of children living in the small spaces has risen as the city's increasingly exorbitant rents mean that the scraps of the rental market are all that's left for some working-class families.

Wendy Phillips is executive director of Dolores Street Community Services, which provides services to the Mission's poor, including families living in SROs. She said that last year, the citywide SRO Families Collaborative worked with 550 families, and that there are more out there who weren't part of the organization's work. Since many families living in SROs have multiple children, the number of kids in the residential hotels is likely higher than the 1,200 found four years ago.

Phillips added that last year, the collaborative found that for every one family who managed to move out of an SRO, three more moved in, filling rooms that previously were occupied by single adults.

'Terrible decisions'

Bevan Dufty, the mayor's point man on homelessness, said many families have no choice, adding that once parents have jobs and kids are enrolled in school, it's not so easy to pack up and leave for a far-flung and less expensive locale.

"Families are really faced with terrible decisions to live in vehicles or couch surf or just try and nest in a single room," he said.

The tiny quarters don't allow space to study, play or have friends over, and don't give parents any privacy. Phillips said babies living in those tiny quarters sometimes lag developmentally with no space to learn to walk or crawl, and children can suffer educationally with no quiet place to study and their nutrition can be poor, with their parents having to cook in one kitchen alongside many others.

Seedy surroundings

And that doesn't include the often nasty underbelly of life just outside their doors. At the Grand Southern Hotel, children are confronted at the entrance with a large poster listing the "house rules," including no prostitution, no drugs and no urinating on the bathroom walls. Out front on a recent afternoon, a homeless man slept on a ratty mattress on the sidewalk, and a giant Budweiser truck sat idling.

"That's the problem - this is what kids are exposed to every day," Dufty said.

Chinas and her family have lived at the hotel for a year, having moved from another SRO hotel that was plagued by drug dealers.

"We heard it was more low-key here," Chinas said. "But it's not worth $1,000."

Her husband works as a butcher at a local grocery store, and her three older children attend public school. She's tried negotiating lower rent with her landlord, but hasn't been successful. The family has been on the waiting list for public housing for five years, so far with no luck. She's looked for other housing, but said it's almost impossible for families in the city these days - especially ones with four kids and two dogs.

So they stay at the Grand Southern Hotel, where the lock on their room's door is broken, the kids have bites on their arms from the bedbugs and mice nibble at the food she stores in the room. Mousetraps lie on the floor near where she sleeps at night.

"The mice are still here," she said. "We've done everything we can."

Despite all this, life at the hotel is actually a little better since city officials and staff with the Mission SRO Collaborative got involved 10 months ago. Community organizers, along with Dufty and Supervisor David Campos have met with the building's landlords to negotiate improved living conditions.

Slight improvement

Plywood was nailed over wide holes in the staircase railings so little kids can't fall through. The previous property manager, who residents say was often drunk and belligerent, has been replaced. The library is parking its bookmobile outside every other week during the summer.

Still, problems persist.

Campos said he toured the building as soon as he got word of the conditions inside.

"I was appalled and really upset that we could have these kinds of living conditions in San Francisco - in the heart of the Mission," he said. "These are families that are just trying to play by the rules - it's not like they're not paying rent."

The building has been owned for decades by Zahira Salem of South San Francisco. Her son, Ata Salem, 28, spoke on her behalf and said the family is always upgrading the building and makes immediate fixes when tenants complain of problems.

'The latest and greatest'

He said that just eight or nine families are raising a fuss and that the residents of the other 50-plus units are happy. He said some families leave food out, attracting rodents and bugs. And when the landlord sends an exterminator, the families don't let him in.

"As long as they cooperate, we cooperate," he said. "We supply them with the latest and greatest."

He said that the rents range from $300 to $1,000 a month, depending on the size of the room and the size of the family and that he thinks those prices are fair. He blamed politicians, particularly Campos, who is running for the Assembly on a platform stressing income inequality in San Francisco, for using the families as pawns.

"It's just not cool, it's all politics," he said. "It's very deceiving the way they do their work."

The Salem family is eager to get out of the SRO business and has put the building up for sale for $6.75 million. They've tried unsuccessfully to sell it at various points over the past 10 years.

Down the hall from Chinas and her brood, Basilia Bautista lives in an equally small room with her husband and three children. A huge poster of Justin Bieber hangs on the wall at the request of her 11-year-old daughter.

They pay $650 in rent out of the money her husband makes installing billboards. Bautista said the smoke detector goes off at all hours for no reason, the old carpet is falling apart and cockroaches infest the room. She's complained, but hasn't gotten much help.

"I'm getting used to it," she said with a shrug.

Heather Knight is a San Francisco Chronicle staff writer. E-mail: hknight@sfchronicle.com Twitter: @hknightsf