Yes, you can definitely take the SAT exam just like any other high school going student, and register online and show up to the test center and take the exam.

Hello

Yes you can take SAT exam even if he/she is home schooled.

You have to register online,Once you're done registering you will get an admission ticket.

You can ask for a fee waiver if you're home schooled from a counselor at the local public high school. one must provide eligibility proof like tax records, public assistance records, or record of enrollment in an aid program  to the conselor.

Hope it helps