It's probably not as many as we would think. The smaller the school, the harder it is to get into the tournament (generally speaking) and the large schools historically have had very few freshmen playing. Lately, more freshmen have the ability to move up, but that was not the case in years past. The school that (I think) has made the most appearances in Des Moines is Dub. Wahlert which has been there 26 different years and they have nobody that I can think of offhand who has played in four tournaments. It is hard enough for a team to get there four years in a row, and then if a team is that good it would seem less likely that many, if any, freshmen would play. I'm sure this list will grow, but it is a pretty elite little group.