Our budget was about $20 per kid. We gave each of them a book of practice tests, and they took a test under timed conditions every week or two during the 2-3 months before they took the real test. Sometimes we sat down with them afterward and reviewed their incorrect answers; other times we left it to them to figure out what they had done wrong. I think they each wound up doing about a half dozen practices tests, plus occasional visits to Khan, and that was all they needed to get comfortable with the test and learn to pace themselves.