Folks, it is parshas Shemini. Yes, I know its Friday, but it is not too late!!
Here's the thing. Teachers tell students the signs of a kosher fish are fins and scales, which as my avid readers know is not accurate at all). The Torach says a kosher fish has "snapir v'kaskeses", which Ramban Vayika 11:9 explains are scales which can be removed by hand or with a knife without ripping skin.
How hard would it be to add this little addendum when telling you children (as young a 5!!) how to know what a kosher fish is?
For your younger yungins, I have a little song to use to help them rememeber (sung to the tune of "Twinkle twinkle little star":
Kaskeses is the way to know
If in my tummy this fish can go
If a scale comes out, and doesn't rip skin,
Look out tummy, its coming in!
But if a scale you cannot find
Your fish might be, a treife kind
Is this too hard for a small kid to learn? It is a Torah commandment to learn how to differentiate between kosher and non-kosher species, an integral part of our MESORAH, and best of all, it might even prevent you kid from buying a treif fish some day...
If you really need to, go here and learn more about the biology of the fish, or ask me to come over and help!