I-20 form not provided by local high school

[immihelp]

Hi...

I'm trying to bring my Thai niece to visit for one academic year and
attend high school. The local school district indicated they "are not
authorized to sign I-20 forms." Student exchange programs have
indicated that by law they may not place students with relatives.

Do you have any advice? How can I get a student (or any other) visa for
my niece so that she can stay with my wife (her aunt) and I and attend
high school for one year?

Thank you.

[immihelp]

You can't bring high schools on I-20.