My friend went to () high school and she/he knows you.
My friend who went to () high school knows you.
My friend went to () high school and she/he knows you. ー 私の友達は〇〇高校出身で、あなたの事を知っています。
My friend who went to () high school knows you. ー（関係代名詞を使った形）
どちらも、会話の中で使えます。参考になれば幸いです。
My friend went to 〇〇 high school and she/he told me she/he knows you.
ご質問ありがとうございます。
・「My friend went to 〇〇 high school and she/he told me she/he knows you.」
＝私の友達は〇〇高校出身で、あなたの事を知ってるって言ってました。
（例文）My friend went to 〇〇 high school and she told me she knows you.// Really? What's her name?
（訳）私の友達は〇〇高校出身で、あなたの事を知ってるって言ってました。//本当に？名前は？
お役に立てれば嬉しいです。
Coco
アメリカ合衆国 
日本 
