I have occasionally referred to my students’ children as my honorary grandchildren. This claim is based on a gemara in Sanhedrin (19b), cited by Rashi on our parasha. The pasuk states: "And these are the offspring of (toldot) Aharon and Moshe on the day that Hashem spoke to Moshe on Mt. Sinai" (Bamidbar 3:1). The Torah proceeds to list only the sons of Aharon, not Moshe, prompting Chazal to explain that "whoever teaches his friend’s son Torah is described by the Torah as if he begot him." A closer look at Chazal’s words may fine-tune our perspective.
First let us notice that the Rabbis do not say that a student is like a child. They say, "k’ilu yelado (as if he begot him)." In fact, the pasuk that is the basis for the exegesis uses the word, "toldot." While this can refer to children, it can also refer to the history of or accomplishments of someone or something (see Bereishit 2:4 & 6:9 with Rashi). Thus, the sons of Aharon were the sons of Aharon, not Moshe. However, Moshe begot them in that he contributed significantly to their development.
Chazal’s statement appears to have an extraneous reference. Why does it say, "teaches his friend’s son" and not simply say, "teaches another." The answer is that the teacher acts best when he works in concert with the parents. Whenever possible, he should try to advance the student on the path the student’s parents placed him. Parents and teachers should be friends, not adversaries. Indeed, the pasuk does not refer to Aharon’s sons as the offspring of Moshe but as the offspring of Aharon and Moshe. It was the joint effort that produced the desired, final result.
Chazal’s statement may also allude to a situation where one teaches another’s child as a favor, not for pay. (Note that Moshe is the source for the concept that, under perfect circumstances, one does not take money for teaching Torah- see Nedarim 37a). This distinction has halachic consequence. The Rama (Yoreh Deah 242:34) limits the rule that one should return a lost object to his rebbe before returning one to his father to a case where the rebbe teaches the son for free.
The end of the pasuk is puzzling, as it says the relationships were true on the day that Hashem spoke to Moshe at Sinai. Rashi explains that this is a sign that the relationship between Moshe and his nephews was forged around Torah, Hashem’s word at Sinai. Historically, this is difficult, as Moshe did not start teaching his students on the day the Torah was given. Rather he had just begun spending three periods of 40 days and nights alone with Hashem on Sinai. We may suggest that when Moshe learned the Torah, he had a clear eye toward teaching it to his students. Thus, even Moshe’s own learning time was considered a preparation for the teaching/begetting that would follow.
In summary, a Torah teacher may consider himself a force in forging his or her students’ personalities. However, he should realize that their parents are partners and that the extent of his own credit depends on his dedication.