The word "osam" in "V'limadtem osam es bneichem l'daber bam" is written missing the middle "vav," so that if you didn't know better, you might read it as "atem." The Chofetz Chaim explains that (believe it or not) a person can get too caught up in the chinuch needs of his children, so while he sets aside time to go over aleph-beis with Yankel and learn parshas Noach with Rivka and doing some mishnayos with Shloymi, he forgets that he also has a mitzvah to learn. The Torah reminds us that talmud Torah is not just about "v'limadtem osam," teachimg them, but also "v'limadtem atem," teaching yourself.
Perhaps the kri u'kesiv also means to tell us that the only way to teach your children to become learners, "v'limadten osam," is by first "v'limdadem atem," being a learner yourself. Embody the practices and ideals you want them to absorb; don't just preach what should be done.
The Rambam writes in Hil Talmud Torah writes that a father is obligated to teach Torah to his child as soon as the child can read a simple pasuk. This is a much earlier age than what we consider the age of chinuch for other mitzvos, e.g. there is no mitzvah of chinuch to buy a two year old a lulav and esrog or have him hear shofar. Also, the halacha of chinuch for other mitzvos is derabbanan; the Rambam here presents the requirement to teach a katan as being a din d'oraysa.
R' Aharon Soloveitchik in his sefer Perach Mateh Aharon explains that the mitzvah of teaching a child is not a function of the normal requirement of chinuch for mitzvos, but is inherent in the mitzvah of talmud torah. In other words, when it comes to lulav or shofar or tefillin the Torqah requires you to do the mitzvah and m'derabbanan, there is an additional requirement to also train your child to do the mitzvah as well. When it comes to talmud Torah, the mitzvah min haTorah is for you to teach your child.
[I don't fully understand the proof R' Aharon brings from the age at which the mitzvah starts. The age of chinuch is not some absolute standard, but depends on the mitzvah -- see Archin 3a. With respect to talmud Torah, even a very young child is already capable of learning something; therefore there the mitzvah starts when the child is very young.]