1.Britishpeople are known being very formal .
2.The school did this to reduce the trouble caused by student fashions .
3.Students are at school to study, not to play .
句1主语省略（可能是people，we之类的单词），谓语know，宾语British people ，being formal是宾补。句2主语the school，谓语did，宾语this，状语是reduce the trouble，caused by student fashion是trouble的定语。句3主语students 谓语are（系动词）at school是表语， to study目的状语 。
回答：句1主语省略（可能是people，we之类的单词），谓语know，宾语British people ，being formal是宾补。句2主语the school，谓语did，宾语this，状语是reduce the trouble，caused by student fashion是trouble的定语。句3主语students 谓语are（
