Who Has the Biggest Feet?

On our way back from the gym B noticed something about V's feet. 

"Hey, I have bigger feet than V!"

"Yeah my feet are smaller than yours."

"I wonder who has the biggest feet?"
"Ms. Jill! She has really big feet."

When we got back to the room they decided we should find out who has the biggest feet. 

How could we measure our feet?

E sat and thought for a minute. 

"Like we have to first count our feet and then we have to know what their temperature is."

This was an interesting solution, but the other kids didn't seemed convinced. She thought again and moved to the center of the carpet across from B. 

Without any prompting E put her feet up against B's. They both looked at their shoes and noticed that the toes of E's were just slightly taller than B's. 

"I have bigger feet than B. I need to sit by you because you [Ms. Jill] have bigger feet too."

C sat down and put his feet against B's. 

"Um mine are like his and we have the same."

Everyone took turns measuring their feet against B's.They agreed that if their feet were bigger than B's feet they needed to sit between him and E, but if they were smaller they would need to sit between B & V. 

As they continued to determine who needed to sit where they also started talking about why their feet were different sizes. 

"Well I am four and so is E so that's why we have the same size feet."

"T has the smallest feet because he is only 3."

"Ms. Jill, you have the biggest feet because you're older than we are!"

"V has small feet too and she's three!"

By the end of our meeting the kids had determined who had the biggest feet and who had the smallest. At lot of their conversations revolved around how their feet correlated with how old they were. Is this true?

Why do people have different size feet? Do you get bigger feet the older you get?