A student in my AS Maths class complained about my teaching blaming me for him/her achieving a U in Exam. The student wrote a letter of complaint to the Head Teacher. I think it was passed on to Deputy Head, who, instead of consulting me or asking me started showing the letter to all the students in the class to try to find out who wrote the letter( it was an anonymous letter) . I don't really have a problem with the complaint but is it correct and professional for Dep. Head to have gone around showing all my students the letter even though only one of them had written it. It came to my attention via students and my concern is that this approach completely discredits me as a teacher . Any thought/ advice? Should I speak to Dep. Head or ask to see the letter. What are my rights?