dunce's cap
noun [ C usually singular ] mainly UK uk/ˈdʌn.sɪz ˌkæp/ us/ˈdʌn.sɪz ˌkæp/ (US usually dunce cap)
笨蛋高帽（旧时学生在学习上屡犯错误需戴的圆锥形纸糊帽）
a tall paper hat with a pointed end that in the past children had to wear in school if they had made many mistakes in their work