I'm not sure if there's a place that any of you know of to find mathematical concept books. Since I didn't know of one I researched many number books and found these to be more specifically about comparing. The Common Core standards that I'm doing right now are:
K.CC.6: Identify whether the number of objects in one group is greater than, less than, or equal to the number of objects in another group, e.g., by using matching and counting strategies.
K.CC.7: Compare two numbers between 1 and 10 presented as written numerals.
If your children already know numbers 1 to 12, I found that giving a pair of students twelve-sided dice really helps them to discuss which number is more and which number is less. Tip: If your students don't know numbers, it's better to give them cards where they can count groups of objects. I made this ten-frame comparing book that works really nicely to clear up any misconceptions about more and less, and to show them how to represent numbers in several different ways. I hope you enjoy this freebie!
I also went looking on the internet for helpful videos and found these:
Finally, I really enjoy using technology in my classroom and these web sites are free and easy for kindergartners to use:
Let me know what you think!