I went to a D rated school, and we had more than enough funding. During my four years in high school there was only one class in which I ever had books that were any older than a year or two. Every class room had some computers, and every department had a rolling cabinet full of 30 Toshiba laptops that a class could use.
Unrelated to funding from test scores, our high school and just about every other one in Florida received massive amounts of money to build stuff. My school constructed 3 huge, state of the art 2 story buildings, a new gym, and completely renovated the main building; effectively doubling the size of the school, reducing class sizes, and making every classroom completely modern. Its been a D school for at least the past 8 years, and is once again this year (I just graduated).
The best way to illustrate that fact that throwing money at problems doesn't always fix them is TASK. The state government decided that since this school had 2,000 students, a massive campus, and more than enough resources yet still doesn't make the grade, something should be done. In my sophomore year they instituted TASK, which is a bull-ogna acronym for something that would somewhere else be called 'home room'. Once a week we met with our TASK group of about 20 students, and did nothing besides make occasion arts and crafts, watch ridiculous videos on things like bus safety, and receive free high-lighters, folders, and lame school T-shirts.
TL;DR? Some schools are just mediocre, and some are situated in bad areas. Giving the school extra money usually doesn't help, especially if they waste it on things like newer computers that are rarely ever used and do the same thing as the computers before them, I.E. Word, Powerpoint, and the internet to copy things to appear on said powerpoint.
[I have no idea what Obama actually says about education.]
It took a while for you to find me; I was hiding in the lime tree.