A resignation letter should be written at least 30 days prior to the effective date of resignation. You do not have to give a reason.In the opening paragraph, clearly state that you are resigning from your position. Need to know how to write a resignation letter for teaching? Then read this guide from an EX-teacher filled with tips and templates! Add contact details, company name, and date. Here are sample teacher resignation letters and templates which cover the structure and tips we shared in the blog. State Your Reason for Resigning. Use a formal business format for the actual letter itself. Notify your manager in person before you submit your formal resignation letter.