Current 10th graders will have to take and pass the MISA (Maryland Integrated Science Assessment) at the end of 11th grade, and are supposed to have completed NGSS aligned Biology, Chemistry, Physics courses, which also include Earth Science.
Blair recommends this track for its advanced students (non STEM magnet): Honors Physics, Honors Chem, AP Bio, then AP Chem or AP Physics senior year.
If this is the recommendation, then I would stick with it, because they should have done some internal alignment to have that pathway make sense internally. It sounds to me like the AP Chem teacher is just trying to fill their class.