Jim Mitchell, a top St. James Parish public school official, says Shell Oil Co.'s decision this week to close its Convent refinery is akin to an uppercut to the head from onetime heavyweight boxing champ Mike Tyson. "We're still in the process of getting our vision back," said Mitchell, the school system's chief financial officer. The refinery is St. James' largest taxpayer, its largest employer and a bedrock of the Mississippi River parish's industrial base that has employed generations of its residents. Sheriff Willy Martin said the complex generates a total of $24 million per year in property, inventory and sales taxes for local governments: about $5 million in sales tax and $19 million in property and inventory taxes.