I don't know chinese very much so if i don't understand your question , then forgive me.
we use "クラス委員長",
but we don't use "クラス班長".
"班" means small group about 4~7 people as picnic group, food preparation group.
"班長" means team leader.
"クラス" means the class room of elementary ,junior high school and high school. about 30 people.
"クラス委員長" means class leader. say also "学級委員長".
"委員" means work of class room job. for example, "飼育委員","図書委員","クラス委員".