The answer is yes. While some of these classes are required prerequisites for college majors, all of them count towards OSU's Baccalaureate Core Requirements. Almost all colleges and universities require students to take a broad range of classes outside of their major field. For instance, all students must take math courses, science courses, liberal arts courses, etc. Outreach Campus has specifically chosen course offerings to meet these types of general core requirements.
Grades are determined in a manner prescribed by the individual instructor.
High school students will be held to the same grading scheme and expectations as regular OSU students who take these courses. For specific information you will need to contact the instructor of the particular course. In both cases, students are trying to prepare for college. There are differences, however. Advanced Placement courses confer high school credit while CTC courses generally do not.