Could also be due to fact that the majority of our students require remedial English and math (sometimes they require READING courses) even though they're local high school graduates.
There's something horribly wrong with education in the U.S. We spend something approaching $20,000/year/student for our local high school and some of the students who graduate are functionally illiterate. The public should expect better results for that amount of money spent.
Many of these recent graduates can't read or write well enough to take Freshman English 101 at a community college (they can't write a coherent paragraph on a placement exam). They can't place into something we call College Algebra (a course which is indistinguishable to what I took as algebra in the 9th grade 30+ years ago). Yet they have NYS Regent's diplomas. What the fuck? I think "No child left behind" is better stated as "No child too damn ignorant to graduate".
Maybe I should start teaching my kids Chinese so they'll prove useful to our Asian overlords in another decade or two.