AOs prefer kids who have been challenged by a rigorous curriculum and demanding courses, and who have done well under those conditions.
Not all public schools are created equal in this country. AOs know the difference. Some are equivalent to privates. Frankly, not all privates are created equal, and AOs know the differences among them too.
The school which they applicant attended will be factored in in terms of its ability to challenge students and its ability to provide advanced courses.