The students who do the work wrong from the start take even more teacher time to straighten out. In sixty seconds you can monitor the entire class. Entering each student's space tends to get them on task at least for the moment. And short friendly words, or clarification, or encouragement are often worth more than fifty minutes of directions to the whole class. Ironically the tendency is to overestimate what students can do and underestimate what they could do.
High expectations tend to be correlated with high achievement.
I am impressed that excellent teachers set high goals. But I am also impressed mainly of these same teachers try to start with students at too high a level. Students need to be successful early to reach high standards later. Attention reinforces negative behavior. This past summer my neighbor's dog was locked up in a side yard while my young daughter swam.