  Lorentz Transformations of Special Relativity are derived from two
postulates: the first is the Principle of Relativity, while the postulate of
invariance of the velocity of light, used in usual derivations, is replaced by
a law of lectro-magneto-statics and invariance of electrical charge. Our
derivation does not require the assumption of regularity conditions of the
Transformations, such as linearity and continuity required by other
derivations. The level of the needed mathematics and physical concepts makes
the proposed derivation suitable for Secondary School.
