West Marin’s largest school district saw a significant jump in the number of students with special needs during the 2013-2014 year. The percentage of special-needs students at Shoreline Unified, now over a fifth of the student body, is roughly twice last year’s state average. Although district officials offered no explanation for the rise, they are legally bound to provide additional staffing for those students—at a time when they must do everything they can to reign…