Ivan Illich said this quote

Skill teachers are made scarce by the belief in the value oflicenses. Certification constitutes a form of market manipulation and is plausible only to a schooled mind.Most teachers of arts and trades are less skillful, less inventive, and less communicative than the best craftsmenand tradesmen. Most high-school teachers of Spanish or French do not speak the language as correctly as theirpupils might after half a year of competent drills. Experimentsconducted by Angel Quintero in Puerto Ricosuggest that many young teen-agers, if given the proper incentives, programs, and access to tools, are better thanmost schoolteachers at introducing their peers to the scientific exploration of plants, stars, and matter, and to thediscovery of how and why a motor or a radio functions.