I will advise you to spend some time in observing if there is any real gaps between the school standard and your girl's abilities. The school syllabuses are not ahead of their levels, so if you find your girl can't complete the assignments by herself with minimal guidelines because of her abilities, not her discipline. Then you may consider to have additional tutoring for those areas.
According to my experience 補習老師 may only help the kids to complete their homeworks but can't ensure their understanding to the materials. In case you really need some information, you may PM me as I know where some of the girls are going.