Judging by the number of learning apps available to classrooms around the country, the education technology market aimed at elementary through high schools is booming.

There are more than 3,900 math and reading apps, classroom management systems and other software services for schools in the United States, according to LearnTrials, a start-up that helps school districts assess and manage these tools.

The money pouring into ed tech tells a different story, however. Despite the volume of novel products aimed at schools, the biggest investments are largely going to start-ups focused on higher education or job-related skills — businesses that feed a market of colleges, companies and consumers willing to spend to promote career advancement.

Venture and equity financing for ed tech start-ups worldwide rocketed to $2.98 billion last year, up from about $1.87 billion in 2014, according to a new report from the research firm CB Insights. Industry analysts attributed the bulk of that increase to seven investment rounds of $100 million or more, none of them for businesses focused on public schools in the United States.