肩(かた)を持(も)つto side with (someone), to support (someone)

先生(せんせい)に肩(かた)を持(も)たれているあの生徒(せいと)は有利(ゆうり)だ。

That student who is supported by the teacher is at an advantage. {to side with (someone), to support (someone)}

上司(じょうし)は一人(ひとり)の部下(ぶか)の肩(かた)を持(も)つわけにはいきません。

The boss cannot afford to side with or support just one subordinate. {to side with (someone), to support (someone)}

弱(よわ)い者(もの)いじめが嫌(きら)いな僕(ぼく)は、常(つね)に弱(よわ)い方(ほう)の肩(かた)を持(も)ちます。

As someone who hates bullying the weak, I always side with those who are weaker. {to side with (someone), to support (someone)}

肩(かた)を持(も)つなら肩(かた)を持(も)つで、全力(ぜんりょく)で私(わたし)のことを支(ささ)えて欲(ほ)しいです。

If you are going to side with me, I want you to support me with all your strength. {to side with (someone), to support (someone)}

常(つね)に中立(ちゅうりつ)であるべき教師(きょうし)はどちらか一方(いっぽう)の生徒(せいと)の肩(かた)を持(も)つわけにはいきません。

Teachers, who should always be neutral, cannot afford to side with or support one student over another. {to side with (someone), to support (someone)}