The number of school districts and charter schools that are privatizing food, janitorial or custodial services saw its biggest increase in more than a decade, according to a report released today. The Mackinac Center for Public Policy, a Midland-based conservative think tank, each year surveys school districts, asking whether they are privatizing one or all of those services. This year, 61% of districts and charters said yes. That’s up from 54% last year. It’s also up from 31% in 2001.