All insurance and/or fringe benefit vendors visiting schools shall contact and secure the permission of the Superintendent (or designee) prior to visiting schools. If approved, the vendor will receive a letter of authorization to present to each principal visited. This letter of authorization does not mandate that the vendor be allowed to meet with the principal; that decision resides with the principal. All other vendors visit a school at the discretion of the principal, no letter from the Superintendent is required. Vendors' visitations to schools shall not be permitted to interfere with the normal instructional and learning program.