你问的英语是英语课吗?
我们的英语已经上了一个半小时.（用完成时）
We have had the English class for one and half an hour.
我们一个半小时之前上的.（用一般过去式）
We started our English class one and half an hour ago.
你同学通常什么时候做作业.:
When does your classmate usually do his/her homework?（一个同学）
When do your classmates usually do their homework?（泛指其他同学）