Human Resources Side Letters - San Bernardino City Unified School District. Letters of resignation should be addressed to the County Superintendent of Schools and directed to Human Resources.Ensure the most current form has been submitted. Our Mission is to Empower our District Leaders through engagement, guidance and support, creating and maintaining positive relations with our employees. In the opening paragraph, clearly state that you are resigning from your position. Learn how to write a professional resignation letter with our step-by-step guide, easy to use templates and helpful tips. An effective resignation letter includes your name, your job title and your departure date. An employee wishing to leave in good standing shall file a written resignation with the appointing authority in the form of a Resignation Notice or a letter.