what subjects are required by law

This is right from the law. You cover this list during the grades 1-6 either each year or at least once during those six years. I seems logical to do the basics like math and language every year, but history can be as required US History or PA History but not every year. Cover those and add other history such as world history, ancient history, etc. Or if you want to take several years to do US History that is good too. YOU are the supervisor of the home ed program.

(1) At the elementary school level, the following courses shall be
taught:
English, to include spelling, reading, and writing;
arithmetic;
science;
geography;
history of the United States and Pennsylvania;
civics;
safety education, including regular and continuous instruction in the dangers
and prevention of fires;
health and physiology;
physical education;
music;
and art.

(2) At the secondary school level, the following courses shall be taught:
English, to include language, literature, speech and composition;
science;
geography;
social studies, to include civics, world history, history of the United States and Pennsylvania;
mathematics, to include general mathematics, algebra and geometry;
art;
music;
physical education;
health and safety education, including regular and continuous instruction in the
dangers and prevention of fires.

Such courses of study may include, at the discretion of the supervisor of the home education program,
economics;
biology;
chemistry;
foreign languages;
trigonometry;
or other
age-appropriate courses as contained in Chapter 5 (Curriculum Requirements) of the State Board of Education.


this is the exact wording in the law.