Since you are going to write a letter to the principal, it should be properly formated. After you write your first draft, read it and proofread your work, omit unnecessary words and use the appropriate punctuations for your sentences. You might want to revise it. It is very important that you should knowhow to write letters especially business letter where formality is required.
Please give me permission to attend your school because [reason]. Please contact me at Email Removed or [phone number] if you require any further information.
Thank you very much for your time and consideration.