Under 18 All Valley Tournament
In the first movie, the tournament is for under 18. How could Daniel, who's supposed to be in college or Mike Barnes, a hired karate expert, allowed to fight?
In the first movie, Daniel has a birthday right before the tournament, which he should turn 18 since he's a senior. If that is the case, the tournament could be 18 and under. If he is really young for a senior, he could have just turned 17. Then the under 18 could still apply (not 18 and under).
Either way, the following tournament against Mike Barnes, he should be either 18 or 19. Since Mike Barnes is a hired fighter, I would assume that he also is not in high school (also he lives with Terry Silver) and probably wouldn't be eligible either.
I would think that Daniel turned 18 in the first movie based on being a senior and the time of year. This would make the tournament really 18 and under. This would also make him ineligible for the next year.