[LDale]

Assuming an involved parent (with the accumulated educational knowledge/value associated with a proper education of their own) rather than purely an "unschooling" approach (which is increasingly more popular, if risky) - this is likely true.

You are effectively providing the student (your child) with a full time, one-on-one tutor (you) which is significantly more effective (even with a less experienced teacher) than an instructor being asked to teach 20/30/40 children at one time.

A teacher in a full classroom of 30 students simply cannot pay attention to a child's advancement as precisely as a teacher working one-on-one.