I work as a math teacher for 11th and 12th grade, and I have the same problem. It's incomprehensible to me, but since I don't teach the grades where you learn fractions, I can't say what went wrong before. All I know is that it is a huge hurdle in higher grades. How are you supposed to do derivatives if the basics are missing!
The fool hath said in his heart, There is a God. They are corrupt, they have done abominable works, there is none that doeth good.
Psalm 14, KJV revised edition
