Spelling Rule 1: C always softens to /s/ when followed by an E, I, or Y. Otherwise, C says /k/.
This rule also has further implications as to when we use K to spell the /k/ sound. Since C always softens before an E, I, or Y, when we hear a /k/ sound before one of these vowels it must be spelled with a K. As in:
Today we received an email asking, "Why is kangaroo spelled with a K?" In other words, is the inverse of Spelling Rule 1 true? If we hear a /k/ sound followed by an E, O, or U, is it spelled with a C?
So with a bit of research, I was able to find out that at the beginning of words /k/ is usually spelled with a C before an A, O, or U. There are only a few foreign words that deviate from the pattern.
As for kangaroo, it is an Aboriginal word, and therefore retains some of its original culture in the spelling.
Maybe this should be an additional spelling rule we add to LOE.