A full set of math flash cards includes the operations of addition, subtraction, multiplication, and division from 0-12. It's a lot of facts. It's a lot of cards to memorize! For this reason, many students never fully learn their math facts, and even if they do, few retain them for instant recall in the later years.
Core flash cards are designed to memorize all math facts in an organized, time-saving way. It works. The system has the advantage of moving quickly and minimizing pain, and is designed to require little or no teacher input. But the real beauty of Core is that it provides an easy way to organize the math facts for quick review each day long after the facts are memorized. Through organized review, your students will be strongest at the same time the average student's recall begins to fade.
Some modifications to the flash cards are provided to save time: is there really any need to memorize "0" or "1" facts, or even multiplication by 11? Not really; once you know the rule, it's easy. Remove these except for a few examples, and you end up with 360 cards.
Also, why not use the Commutative Property to save time (remember, 2x8 = 8x2)? This cuts your flash cards in half (note that subtraction and division are handled by grouping operations; that is, 8-2 to 8-6 and 28/4 to 28/7). Of course, every card must still be learned, but there is certainly no reason to review 2x3 and 3x2 on the same day! If you know one, you will know the other.
For this reason Core flash cards are split into two stacks of 180 cards (called Highs and Lows). By alternating between Highs and Lows each day, you still are, in effect, learning every card every day and yet paring the cards down to a reasonable level.
The final advantage to Core: each high/low stack is organized into six color sets for organized practice. Six different colors in each high/low stack makes only thirty different cards per set. At two seconds per card, each set is polished off in a minute! To the child, this is a light at the end of the tunnel, and makes for easy, organzied, continuous review long after the cards are memorized. Therefore, when it's time for SAT exams, your student doesn't just know his stuff - he knows it, backwards and forwards, for very little time investment.
A Better Flash Card System