In the 2004-2005 season, DeLaSalle didn't win a game until their 4th game. Their first win was against Archbishop Mitty of San Jose, CA. They did not play Long Beach Poly that season as depicted in the movie.
The trivia item below may give away important plot points.
The game against Long Beach Polytech was actually during the 2000-2001 season. They beat Poly 28-15. The game was also at night, not during the day as shown in the movie. Maurice Jones-Drew was on the team when they played Long Beach.