我是那个高中的第一届学生。
I am the 1st year graduate of that senior high school
I am the 1st year graduate student of that senior high school
我认为要加一个YEAR，届其实就指什么年毕业的学生。比如05届学生。
I am that high school's first session of students. That high school isnewly opened.
I was the first high school students. That the new high school is open.
the first time
