Complex sentence: Melvin Sneedly breaks his promise and tattles on George and Harold and infuriated, Mr. Krupp puts George and Harold in detention for the rest of the school year, with the threat that they'll be suspended if they leave the detention room once for any reason.
Split into simpler sentences: Melvin Sneedly breaks his promise and tattles on George and Harold. Infuriated, Mr. Krupp puts George and Harold in detention for the rest of the school year, with the threat that they'll be suspended if they leave the detention room once for any reason.