Should a charter school have a union?

The charter school movement was started to change the status quo of education. Charter schools improve student achievement and provide an alternative education for parents and students which creates laboratories of innovation with the least restrictions possible. The goal is to maximize student achievement within the boundaries of their charter. Do unions represent restraint to change?  The purpose of unions is to maintain or improve the conditions of employment according to the “History of Trade Unions.” Since to maintain is the opposite of change and to improve conditions of employment can conflict with the goal of improving student achievement, it is easy to see why unions could hinder student achievement in the charter school setting.