Surprisingly, no. Because you work under contract for a school district, anything that you create for use in the school, becomes the schools property. This is because creating worksheets, units, etc. is considered part of a teachers job. This concept is known as “work for hire”. If a teacher is interested in creating a book or other creation in order to sell or use for other distribution purposes, that teacher should get a written agreement with their district for the copyright. If a teacher works for their district to create a curriculum or unit of some sort, and that teacher wants copyrights or to share copyright for this creation, the teacher should sign a contract with the district agreeing to do this.
Simpson, C. (2005). Copyright for schools: A practical guide. (4th ed.). Worthington, Ohio: Linworth Publishing, Inc.