From carpools to practices, a growing number of families are relying on the services to schlep kids to and from school, after-school activities and other destinations. Demand is strong enough that several startups, including San Francisco’s Shuddle are operating, backed by millions in venture capital, to serve the market for transporting children. “Ride-sharing companies will look for any opportunity to demonstrate to people that they can be an alternative for any situation that they encounter in their life, including back-to-school,” said Thilo Koslowski, lead automotive industry analyst at technology research firm Gartner. While San Francisco companies Uber and Lyft require users to be at least 18, that hasn’t stopped some parents from letting their children use the services on a regular basis, creating a gray market for UberBlack and other ride-hailing offerings, according to industry analysts and media reports. The ride-hailing industry has grown exponentially over the past few years on a network of private drivers as an urban alternative to taxis and public transportation. Several competitors, including Shuddle and HopSkipDrive, are actively offering rides to children using a staff of mostly female drivers who double as caregivers, with safeguards to try to get parents over the hump of putting their kids in cars with strangers. Shuddle, which began operating in October, has raised $12 million and has built a crew of 200 mostly female drivers — moms, teachers, nannies and other caregivers — to transport kids throughout the Bay Area. Shuddle CEO Nick Allen, 36, who helped start ride-hailing service Sidecar, said demand is already building for back-to-school bookings. Jeremiah Owyang, analyst and founder of Silicon Valley’s Crowd Companies, said that while there is clearly a market, limiting ride-hailing services to children may be too narrow to sustain a business in an as-yet-unprofitable industry. If they could couple that with other services such as tutoring or food delivery for moms, then maybe they might have a broader segment to choose from. Drivers are trained and empowered to sign kids out of school and help them check in at after-school activities.