Our Gemara on Amud Beis refers to a teaching approach repeated several times in Shas, known as,“To sharpen the students”. A teacher may say over something that is obviously incorrect in order to stimulate the students to question the teaching. The idea is to keep the students on their toes and create an environment where all ideas are critically challenged and not taken for granted. In other words, the teacher “serves softballs” that are obvious enough that average students will be able to cast a mistake. This emboldens students to become more sophisticated and challenge the rabbis teachings even more.

There is one instance in Shas where even though the same idiom is used, “לחדד בה את התלמידים” to sharpen the students, it has a different import.  In Eiruvin (13a) Rabbi Akiva praises an argument offered by a student. At first, it was assumed that Rabbi Akiva’s praise of the student’s assertion was synonymous with his approval of its correctness. However, Rabbi Akiva’s next statement showed that he did not agree. The Gemara resolves this apparent contradiction by understanding that Rabbi Akiva was praising the student’s statement “in order to sharpen the students”.  Tosafos and Ritva (Op. Cit.) both point out that here the sharpening is not to encourage the students to challenge and question, but to encourage them to speak up their novel ideas and opinions. 

My father Z”l, an educator and trainer of teachers for more than 60 years had certain similar practices that he would encourage his teachers to employ with students.  He did not like when a teacher told a student their answer was “wrong”. No matter how off base the child’s answer is, find some way to indicate how it is partially correct and on the way to the right answer.  Such as, “Ok, so this shows you are trying to explain how… or this is your way of answering such and such…Here is why we still need to develop a better answer because of XYZ…” My father also found it unnecessarily harsh to grade with a red marker.  He would say, “There is no need to literally underline the child's mistake in red ink.  It is sufficient to mildly mark it as incorrect.”  These ideas are not false flattery or overly indulgent of the students, We see from Rabbi Akiva’s behavior toward adult scholars, that everyone needs encouragement and a soft touch.