可以报境外的考试。

网上找到一个解答，移过来供参考：

“If you are a home schooled student, you register for the ACT the same as everyone else, either by paper or online. The only thing that will be different will be when you fill in your ACT high school code.

For home schoolers in the United States, it is a universal number: 969-999

Generally, everything else will be the same, though there is a procedure to follow in case you have problems finding an acceptable ID. I bring this up in particular because most students can use their school photo ID, but as a home schooled student that won’t be an option for you.

On test day, you are required to bring an acceptable photo ID and your printed ACT admission or standby ticket with your photo printed on it.”