I am preparing to take the high school teacher qualification certificate exam. Do I need to prepare high school course content or university course content for the trial teaching?

The trial lecture is actually to test your actual teaching ability. The corresponding scope is the teacher qualification and type you are applying for.

Example:

If your teacher applies for qualifications in high school Chinese, then the scope of your trial lectures will be the Chinese language of all grades in high school. Lesson Plans. So it's from high school, not college. You can rest assured about this.

Best wishes