It's hard to get an 18 year old interested in listening to John or Martha King and/or the Sporty series for instrument written test training. I'm not saying they are bad, but based on some opinions in the forum, my son demo'd those and also Pilot Training Solutions material. My son felt PTS was the only one geared towards his style of learning. Luke, the chief pilot with PTS has been more than responsive by phone and email when my son had questions. I have no affiliation with PTS other than my son being a satisfied customer.