"Middle school classmate" 用英语可以说作 "middle school classmate"。这个词组来源于英语中 "middle school" 意为 "初中"，"classmate" 意为 "同学"。
例句：
I have a lot of fond memories of my middle school classmates. (我对我初中的同学有很多美好的回忆。)
I'm going to a reunion with my middle school classmates next month. (下个月我要和我初中的同学重聚。)