The game started off poorly for the Spartans as they gave up five runs before the game's initial out was recorded. But they battled back, taking a 9-7 lead, before Bosco tied it up in the sixth.
But a passed ball in the seventh inning was the difference.
For Rosemead High, the season did not start out well as the Panthers were crushed, 8-0, by tournament host Montebello High.
Junior righty Rafael Garcia took the loss for Rosemead.