Typically, these apps let parents enroll their kids, pay for day care and get daily secure messages — with photos — showing them how and what their children are doing at school.

Now, schools, day care centers and even summer camps and Sunday schools are going digital with apps from start-ups including Brightwheel, Kangarootime, Kinderlime and Tadpoles.

Parents used to rely on paper to sign kids in and out of day care, make payments to schools and get crucial updates from people they entrust with their youngest family members.

Today, there are even more day care centers operating in the U.S. (740,000) than single-location restaurants (183,000), according to research from IBIS World. And day care centers generate around $50 billion in revenue domestically each year. Typically, for families with kids under age 6, child care and education represent their second biggest household expense.

The size of the market and transactions in it have attracted venture investors to this space.

Most recently, Brightwheel raised $21 million in a series B venture round led by Bessemer Venture Partners. (Omidyar Network, Chan Zuckerberg Initiative, GGV and others also funded the company.)



To make money, Brightwheel — which first garnered attention on the business reality show "Shark Tank" — charges preschools around $2.50 per kid per month.

Its app stands apart because, in addition to giving parents a way to connect with care centers, Brightwheel has also built in early childhood "learning assessments." These help day care operators to make sure they're keeping up with the quality of education recommended in their state's early learning frameworks.

"Investors used to roll their eyes at me, frankly," said Brightwheel founder and CEO Dave Vasen. "Why would a preschool need software? But then you remind them this is software as a service that makes things easier for businesses and better for customers. It's like Open Table was for restaurants or MindBody for fitness. Parents find this is an Instagram-like experience. And they want that."

Disclosure: CNBC owns the exclusive off-network cable rights to "Shark Tank."