Few students found the secret,as had the teacher told much
尽管老师讲了很多,但鲜有学生发现那个秘密.
这是as的特殊用法.as引导的让步状语从句中,动词或助动词要提前,这里把表完成时的助动词HAD提前,并省略了through. 还原原句为 Few students found the secret,as through the teather had told much.