Every owner, tenant, or operator of a farm employing thereon as agricultural labor any parent or guardian having minor children in his immediate care and custody shall post at a conspicuous place on the property or place of employment where it may be easily read by those employed, a notice stating that minor children are not allowed to work upon the premises unless legally permitted to do so by law and unless permits to work have been secured by the minor children from duly constituted authorities. All such notices shall be printed in both the English and Spanish languages.