Online schools are growing in popularity these days, along with MOOCs, or Massive Open Online Courses, where students can simply enroll (or just take the course for free) and receive online education. In some cases, they can receive full certification in a particular subject area. However, not all universities will accept the validity of the content provided by a MOOC and not all MOOCs are created equal. Each person (and each institution) will have to decide whether or not a MOOC or online school is providing quality knowledge.
Here is a link to an infographic showing how the increasing prevalence of online schools is transforming education: