A teacher would have as much obligation to report government fraud as anyone else would. Whistleblowers have various laws they can look to for protection from retaliation for reporting fraud or corruption or health and safety violations, but the effectiveness of these laws will vary from state to state and case to case. To protect your job, if that is what you are worried about, or to remain anonymous, if that is what you are worried about, you can use a fraud hotline or you can report the fraud to an outside source, such as the media, an attorney, or law enforcement officials.