Typically a person needs all the current academic records from the school a child is currectly attending. This would include current classes and grades; previous grades and courses; testing records; cumulative records, if possible; special education records (if relevant). Critical information needed includes an official copy of your child's birth certificate and a local address (envelope mailed to you to show your current address).
Don't hesitate to email schools directly for their local enrollment procedures.
Hi, Are you asking how your kids can be enrolled in a U.S. high school if you aren't U.S. residents, or how your kids can enroll in a high school in your current location outside the U.S.?
If the former: I suggest contacting the school district for the high school you wish to enroll your child. Find out their specific policies and procedures for school enrollment, as these vary across districts and states. You can use SchoolFinder to research the contact information for U.S. high schools and their school districts: http://www.education.com/schoolfinder I would narrow your search by focusing on the districts near the residence where your children would be living while attending the U.S. school.
If you are asking about enrolling your children in schools outside the U.S.: I suggest contacting the U.S. consulate for that country/region, and follow their advice for U.S. citizens seeking to educate their high school-age children in that country. Alternatively, you could contact the local education agency within your current country's government, and/or talk to other U.S. expats with children living and schooling there.