This is the approach commonly used in private schools.
It is where they feel the most comfortable because the books come pre-designed for a standard school year with material arranged for 5 days a week.
People who have a teaching background will often go for this approach because it is familiar and often the only way they have ever taught.
It has all the information needed to prepare a student well for college academics because colleges and universities will most certainly use this teaching approach in most of their classes.
The greatest drawback is that to someone who does not come with a teaching background in the given subject, the material may seem complicated and time-consuming.
Because the traditional approach publisher makes the assumption that the parent has a background in teaching, they will often omit basic instructions or explanations of the course's foundational material believing it is not needed.
This may make the parent feel like they are missing something if they do not understand why the material is teaching something a certain way.
Many of these curriculums have been around for quite a while, so the material in the curriculum will often be well written.
However, the material will expect average class-room allotted time for teaching the subject, so it may feel overwhelming to both student and parent to spend 45-60 minutes on just one school subject.