Many dental assistants have had nothing more than on the job training. Dental Assistants SHOULD be required a certification program to work in a dental office but it is a different job with different requirements, skills and a different knowledge base.
Dental Hygienists have at least a two year degree with courses in anatomy, physiology and microbiology, along with specific courses in head and neck anatomy, histology and pharmacology.
It is against our belief to, "Do no harm" to allow assistants to scale. If a dental assistant wants to scale, then they should go to school to become a dental hygienist. Let's do what is best for the patient.