How do I pack this in a polite email?

I have to write to my teacher that I can only attend the secondary school part-time because I have to prepare for an esport event (fortnite).

Of course, I would catch up with the homework by homework.

How do I pack this in an email?

You can save the effort. If you still have compulsory education, you can't just go to school part-time.

It may be possible to stay home for a day when the school plays along. No more.

Last year made a conclusion

No matter how you want to pack that into an e-mail. That's what you do in a personal conversation.

I only guess that your teacher will explain: You have to attend school until the age of 18 and beyond until the end of the school year. If you miss, you risk the dismissal from high school and then you may attend the vocational primary school year or the vocational preparation year (compulsory).

Note:

https://www.pcgames.de/Fortnite-Spiel-16272/News/Spieler-des-Australian-Open-Events-warten-noch-immer-auf-ihr-Preisgeld-1280837/

"You have to attend school until the age of 18" yes is clear

Find yourself a more meaningful task than to give such a nonsense of you here.

5 days ago you still had pancreatic cancer, then you were worried about your receding hairline, about 50 cheeseburgers, your undersized testicles and that your parents want to kick you out without training or job.

And today you visit the upper school…

And tomorrow I'm a pensioner