When you think about the number of standardized tests a student just starting school today will take by the time they finish college some 17 years later, it's pretty remarkable. In the US alone there are over 300 million standardized tests administered each year. Globally, the number is over 1 billion tests a year. Current estimates of the standardized test prep market range between $5-7 billion, with a potential market of about 10 times that and growing at about 10% a year. (Sources: Eduventures, IBISWorld)
Test prep has been a growth story for quite a while, but still only about 10% of students taking those tests pay for prep services such as tutoring, classes or online study tools. Another 40% or so shell out for study guides, quiz books and other self-study material, but that still leaves a whole lot of students out there.
One more number to boggle the brain is the $1 trillion US educational market. We have two trillion-dollar-plus industries in the US: Health Care and Education. The private-sector's share of this pie is growing at a tremendous rate - though it's anyone's guess to exactly how much each year.
There's a reason that the education and learning is a space is one to watch. Web tools are rapidly transforming the traditional physical teacher/classroom model into a vastly more interactive and accessible platform. I think we're really just at the pioneering phase in online learning. The incredible growth of many of the online colleges in the past ten years like the University of Phoenix, DeVry, etc., is really just phase one of the coming revolution. The way our children learn in the next 20 years is going to rapidly change as new tools literally open up the world to them in ways once unthinkable. It won't be out of the question for a 4th-grader to learn Mandarin online in the middle of the school day on a school computer from a teacher in Mainland China. Or perhaps a student in the Congo to learn chemistry from a teacher in a lab in Chicago.
There are a number of different ventures out there looking to make this happen, and there's plenty of room for many different approaches. I think the ones that truly connect people to one another will rise to the top. Those that simply offer content will be fighting a losing battle - learning is interaction. Great teachers are essential and they exist all over the world. Now we just need to connect the students with them and each other.