LYNN – You wouldn’t have known it by its reaction Wednesday, but the St. Mary’s softball team clinched a share of the Catholic Central League/Large title with a resounding 12-3 victory over Arlington Catholic. St. Mary’s and Cardinal Spellman are co-champs after Spellman swept a doubleheader with Austin Prep, also on Wednesday.”It’s just unbelievable,” said coach Colleen Newbury, referring to her first title of any sort since 2002, when the Spartans won the Division 3 North crown with a win over Shawsheen.The score may indicate that the game was a wipeout, but it really wasn’t. The Spartans hung on to a 3-2 lead until the fifth, when they put up three more runs; and then finished the deal an inning later when they scored six more.It was only last week that St. Mary’s Katelynn Fanning and AC’s Kelli Reardon got caught in a fierce mound duel, with the Spartans taking a 1-0 win in extra innings. Two nights later, St. Mary’s lost a slugfest to Cardinal Spellman, 14-10, but Newbury feels that game served as a confidence-booster for Wednesday’s.”We kept coming back in that game,” she said. “And we scored five runs in the last inning. So they’re fighting back, and I think that gave them confidence today.”St. Mary’s would need the confidence. A key error in the third inning gave the Cougars a 2-0 lead, and the way Reardon was pitching, it looked as if the two runs would be enough.But St. Mary’s broke through in the fourth with three runs to take the lead. Christina Burri led off with a dribbler that stayed fair as it rolled down the third-base line. Erin McAndrews followed with a single, and Kristen Mondello (5 RBI) laced an opposite-field triple to even the score. She scored when Ariel LaRosa sat on a tantalizing changeup and roped it into left for a single.The Spartans doubled their output an inning later, thanks to Mondello (a single for one RBI) and Maria Nazzaro (who knocked in the third run of the inning when she reached on an error).But the real fireworks came in the bottom of the sixth when St. Mary’s sent 10 batters to the plate. Once again, Mondello and LaRosa were in the middle of the rally, with runs batted in.”We had some good swings at the ball,” Parker said. “We were level with it, and hit some line drives.”Fanning was the beneficiary of the offensive firepower as she coasted through seven innings, allowing only five hits.