My 3rd years in JHS finished their textbook, so I made a writing activity for them to prepare for high school, in which they are encouraged to use English/grammar they already learned.
This activity is about your "treasure" - an object important to you, and explaining why. It works best if you do a "Show and Tell" as a demonstration. I brought a stuffed animal from my childhood in Japan, and my students were really excited to see it for some reason, lol. I also accompanied it with a Powerpoint. First, I showed them my treasure, and I explained to them why it's important to me. Then I showed them what I said on the screen, and a few students used it as a reference for their own writing.
After that, they should be making their own "MINI MAP" of what they want to write. Of course writing in Japanese is okay, as long as they can translate what they want to say into English they already know. I would give them about 5-10 minutes to do this.
Then, the rest of the time they should be writing. I put my 3rd years in groups so they can help each other and so its easier to help them. :)
That's all! You can obviously elevate this and have them do presentations, or a real "Show and Tell", but I just stuck with the writing activity.