"Teaching Thoroughly" Vs. "Teaching"

Dear Rabbotai, I have a question. It says in the first paragraph of the Shema "You shall teach it thoroughly to your children", but in the the second paragraph, it says "And teach them [Your children] this". Why the difference? Sincerely, Joseph.

In the original Hebrew, these are two totally different verbs: “l’shanen” means to repeat/review diligently (rather than “thoroughly” as you have seen translated) until the children know (!) it basically by heart (Kidushin 30a and Rashi: on the tip of their tongue), as opposed to “l’lamed” which means to teach until they understand (!). The first is usually done at a younger age, to know the Torah word-by-word even externally, and the second is to understand, internalize and identify with the Torah, which is a later and deeper stage of education (see Avodah Zara 19a).