Former Homeland Security Secretary Janet Napolitano, who left the Obama administration to take over the University of California school system, told The Washington Post she is “deeply skeptical" of President Obama's proposal to rank colleges and universities based on value.

“I am deeply skeptical that there are criteria that can be developed that are in the end meaningful because there will be so many exceptions, once you get down to it,” she said. “It’s not like, you know, you’re not buying a car or a boat. And so I hope to have the opportunity to engage in a productive way in this discussion.”

This summer, Obama announced that the Department of Education would create a new ranking system that grades universities on their value to students, providing applicants with a clearer idea of which schools give students the best bang for their buck.

He also proposed tying federal aid to the rating system, arguing that the federal government should not subsidize schools "who have higher default rates than graduation rates."

"It is time to stop subsidizing schools that are not producing good results," Obama said.

But Napolitano said she did not believe there were a lot of "apples to apples comparisons" to be made.

The Department of Education is still developing and fine-tuning the rankings system, which isn't expected to be unveiled for another year.

White House officials said the rankings would grade universities on their ability to hold down tuition and student loan debt, and measure costs against post-graduation employment rates. They have also promised to solicit input from students and educators as they develop the system.

Obama argued the rankings would empower "students and families to make good choices," while also incentivizing schools to hold down costs — much as popular rating systems like the U.S. News and World Report rankings lead universities to prioritize certain programs and goals in order to gain an edge on competitors.

Napolitano said she had not yet spoken to Education Secretary Arne Duncan about the plan.

Napolitano took over the California university system at the beginning of October. She last publicly met with President Obama during an immigration rally in California late last month.