Modern K-12 teaches primarily an Euler level conceptual approach to natural numbers and fractions, i.e. pointing and assertion not logic. There is a coverup that the Grassmann, Dedekind and Peano Axiom approaches exist.
This coverup is damaging to students. They are made to feel that they are supposed to understand something that in fact is not even there. There is no conceptual explanation of natural numbers and fractions in Euler that holds together and leads to the known properties.
That was developed by GDP. This is concealed from students. This is a coverup. It is a joint coverup of the math ed training in college, standards committees and the few teachers in the know.
The coverup is not to help those deceived, but to harm them. They are made to feel they should understand natural numbers, addition and multiplication and fractions conceptually, when in fact no such explanations are given. Thus they are made to feel hopeless at math. This is deliberate.
All coverups are intended to make the victims give up trying to find the truth. Covering up the existence of the GDP approach to natural numbers is intended to make students not look for it or try to understand it.
This applies to parents as well. Parent control may in fact be the main reason for the coverup. Keeping parents ignorant of this, means the students and parents are unable to understand K-8 math and thus are unable to criticize the teachers and education establishment.
Elementary math is kept a deliberate mystery in order to keep it in control of a priesthood in the form of a labor union. This union wants to be unaccountable to parents. Keeping parents from understanding elementary math lets the teacher unions tell parents that it is a mystery that requires initiation in schools of math ed in college and years of experience under the tutelage of experienced teachers to understand elementary math and how to teach it.
All of this is false. Elementary math is not even understood by most teachers conceptually. But this fact is concealed from parents. This is information control to keep parents off.
The Peano Axioms empower parents by giving them the concepts of elementary math. Once they know these exist and are not taught in school, the credibility of the schools, teachers and teacher union is destroyed.
For over a century, the schools have concealed this. They have exercised the worst type of Mandarinism, one where the lie harms the client. The concealment of the math behind elementary math is such a harm.