It is unlawful for any person to do any act forbidden or fail to perform any act required in this chapter. The parent of any child and the guardian of any ward shall not authorize or knowingly permit any such child or ward to violate any of the provisions of this chapter; provided, that no violation of this chapter by any child under the age of 16 years, or by a parent or guardian of such child shall constitute negligence per se in any civil action brought or defended by or in behalf of such child. (1961 code § 11.60.090.)