When "Scholars" (youth who have a solid Core and Love of Learning under their belt) do an assignment, either say "great work" or "do it again." You can help them, but have them do most of the work and never accept a low quality submission or performance. [Note that we're talking here about more mature students, usually at least 12 and older, not of toddlers and children.]
Parents often worry that they aren't really experts, so they hesitate to enforce high standards. And teachers sometimes feel too busy to give assignments repeat personal attention. For young children, the Core and Love of Learning are more important than the conformity or quality of work.
But at some point in their development you will do them a huge favor if you set up a system of standards togetherand then abide by it. The key is coaching.
Think about it. The places where the conveyor belt system gets professional level quality are where they have coaching--athletics, drama, debate, music, etc. This is mentoring, and it is personalized. Students, say the quarterback or the trombone player, are expected to work on it over and over until they get it right. Do the same in academics, and the result will be world-class scholarship.
Quality, not Conformity 
