According to news articles, it sounds like a tennis coach, Mark Riddell, is the person who took or changed most of the tests. It seems there were a couple different methods. In one example, he would fly into Houston and the actual proctor there would facilitate the situation so he could change the tests. Even if the student was in CA, they would schedule the student for the test in Houston. In another example, he would fly into CA and act as the proctor and then help while the student took the test or make changes afterward. The news said he was gifted at calculating his test answers to achieve the increase in score the student needed, but not so much improvement it would be called into question.