The idea
It should not be against "the law" for teaching assistants to teach, just as it is not against the law for unqualified accountants to keep your accounts or for unqualified lawyers to give you legal advice.
The law is protectionism and is unneeded as the market will resolve it. If parents are unhappy with Teaching Assistants giving regular core teaching ( and I know some fantastically able Teaching Assistants) then they will use the Governors forum or feedback through School assessments to express their dis-satisfaction.
Protectionism for supply teachers (often the worst examples of their profession) can only benefit Union power.
Why is it important?
The law is protectionism and is unneeded as the market will resolve it. If parents are unhappy with Teaching Assistants giving regular core teaching ( and I know some fantastically able Teaching Assistants) then they will use the Governors forum or feedback through School assessments to express their dis-satisfaction.
Protectionism for supply teachers (often the worst examples of their profession) can only benefit Union power.