Sorry I know it's short notice. My son wants to focus on his studies so we need to finish our lesson with you.
Sorry I know it's short notice. My son wants to focus on his studies so we need to finish our lesson with you.
「急ですが、息子は勉強に集中したいのでレッスンは終わりにしたいです。」
focus on one's studies で「勉強に集中する」
finish ... with one で「人との…をおしまいにする」
Sorry but my daughter will be quitting her clarinet lesson with you because she needs to concentrate on her schoolwork. I hope you understand.
「すみませんが、娘は学業に集中する必要があるので、クラリネットのレッスンを辞めます。」
quit one's xxx lesson で「xxxレッスンを辞める」
concentrate on one's schoolwork で「学業に集中する」
ご参考まで！
"I’m sorry for the short notice, but we’d like to stop the clarinet lessons."
"I’m sorry for the short notice, but we’d like to stop the clarinet lessons."
"We’ve decided to stop the clarinet lessons at the end of December."
「突然ですがクラリネットのレッスンを辞めたい」
**short notice（急な連絡）への謝罪**を入れるととても自然で丁寧です。
カナダ 
アメリカ合衆国 
