Prior Educational Resources Ltd. began as a small home-based business from a vision of Roger Prior. Roger began teaching senior biology in BC in 1976, and twenty-two years later he began to compile and distribute his sets of study notes for some of the more difficult units in Biology 12. These notes became so popular that he developed the rest of the materials required to complete the earliest version of Biology 12 — A Student Resource.

In 1999, working with a local printer in Trail, BC, where he teaches, Roger ordered sixty copies of his book. As this was happening, word about the book was getting out, and before the first printing was even complete Roger had to expand the order to 200 copies. Shortly afterwards, more copies had to be printed, then in a few weeks more again. By the fall of 2002, thousands of students had gained the benefits of using the second edition of Biology 12 — A Student Resource.

In the spring of 2003, as the staff set to work on the preparation of a website and study guides for Biology 11, it became apparent that they needed to incorporate, and Prior Printing became Prior Educational Resources Ltd. By 2004 the Biology 11 resources had rolled off the presses, and the website was posted and undergoing its first wave of revisions. In the summer of 2007 the staff completed and published the fourth edition of the Biology 12 Study Guide and its supporting resources.