H.L. Strack and Gunter Stemberger, Introduction to the Talmud and Midrash: Second Edition, trans. and ed. Markus Bockmuehl (Minneapolis: Fortress, 1996) 260.
Sifra, Aramaic 'book', designates the book of Leviticus, because in the old Jewish school system this was the first book, with which instruction began: R. Issi justifies this in LevR 7.3 (M.156) by saying that children and sacrifices are pure, and the pure should occupy themselves with pure things.
I looked up the passage in my Judaic Classics Library and could not find it, for whatever reason. Why start Jewish kids out with Leviticus? Wouldn't it be more entertaining for them to hear stories, like the ones in Genesis, or Judges, or I-II Samuel? That's how my dad and mom taught me the Bible. We listened to tapes that dramatized Bible stories. I still remember Jacob crying out, "Joseph has been eaten by a wild animals!" Or Shadrach telling Nebuchadnezzar that his golden image was "just a hunk of ugly junk outside the city wall."
But, on a certain level, Leviticus does make sense to me as the first biblical book that children learn. Why? One reason is that I learned through ritual. As Armstrongites, we kept the biblical Sabbaths and feast days (or so we assumed), and that internalized certain concepts within us (though, of course, many kids raised in the Armstrongite movement depart from it when they become older). So I'm not surprised that Jewish kids read about the rituals that they and their family performed. They approached Leviticus with some knowledge of what the book was about.
Second, the book is pretty simple. Unless one probes it deeply, it won't appear all that exciting, but it's simple enough for a beginning Hebrew student to read. It has numbers and animals, like Sesame Street, or those books that teach kids how to count.
I'm not sure what their teachers did when they got to Leviticus 18 and 20, however, the chapters about perverse sex! Rabbi Issi wants the pure Jewish kids to occupy themselves with pure things, like the sacrifices. In a sense, I can see his point, since Leviticus is all about God's order in terms of his sanctuary and worship. An innocent child not yet exposed to the horrible things in life can perhaps handle that. But there are also chapters in Leviticus that talk about the darker aspects of life. Not only are Leviticus 18 and 20 about perverted sex, but Nadab and Abihu get killed, and the curses of Leviticus 26 can give adults nightmares, let alone children!