When I visited a high school in Australia, I foundnoticed the students were doing something different from students in Japan. When I visited a high school in Australia, I noticed the students were doing something different from students in Japan.

When I visited a high school in Australia, I founnoticed something different from Japan. When I visited a high school in Australia, I noticed something different from Japan.

When I visited a high school in Australia, I foundsaw something different from how things are in Japan. When I visited a high school in Australia, I saw something different from how things are in Japan.

The studentsy were using pens, instead of pencils. They were using pens instead of pencils.

The students were using pens, instead of pencils. The students were using pens instead of pencils.

The students were using pens, instead of pencils. The students were using pens instead of pencils.

We call them "sharp pencils"." We call them "sharp pencils."

If you use a pencil, you can erase what you have written, but if you use a pen, you cannot. If you use a pencil you can erase what you have written, but if you use a pen you cannot.

And I thoughtThen I wondered if European or American high school students use pens, too because Australians do. Then I wondered if European or American high school students use pens, too.

This is simpler and I think it still makes your point.

And I thoughtI wondered if European or American high school students use pens too because Australians do. I wondered if European or American high school students use pens too.

"Because" is used when one thing is a reason for another. You could say, "Because Australia, Europe, and America are similar culturally, I wondered if European and American high school students use pens too." Or "Because I saw Australian students using pens, I wondered if European and American students use pens too."

And then I thought that European orand American high school students probably use pens too because they are similar to Australians do. And then I thought that European and American high school students probably use pens too because they are similar to Australia.

"Because Australians do" sounds a bit vague in this context; I don't know if the revision correctly conveys what you were trying to say.

Let me know what high school students in your countries use to write with! Let me know what high school students in your countries write with!

Let me know what high school students in your countries use to write with! Let me know what high school students in your countries use to write!