DeVonta Nelson, 19, is seen in the career center at T.C. Williams High School in Alexandria with his college acceptance letter from Johnson and Wales, where he plans to go to culinary school. (Dayna Smith/The Washington Post)

“It’s too long.” “I don’t need it.” “Isn’t it too late?”

Seniors at Alexandria’s T.C. Williams High School offered such reasoning this week to explain why they had not filled out the Free Application for Federal Student Aid, the main form prospective students use to gain federal financial help to attend college.

As educators and politicians work to increase college attendance across the country, they often focus on a key barrier to a higher degree: money. Studies show that students who apply for financial aid are more likely to enroll in and graduate from college, particularly as tuitions increase.

That’s how a simple form has come to be seen as an important gatekeeper to higher education. The FAFSA determines whether students will be eligible for a share of more than $150 billion in federal grants, loans and work-study funds, and informs decisions about state-based or institution-based aid.

The Obama administration has taken steps to make it easier to apply by streamlining the online form, so it can be filled out much more quickly. And between the school years starting in 2008 and 2012, the number of students who filed the FAFSA increased by 33 percent, to 22 million.

Yet millions of aspiring college students across the country still don’t apply for federal aid. An estimated 2 million students who did not file the FAFSA in 2011-12 would have qualified for a Pell grant, according to Mark Kantrowitz, an expert on college financing who recently wrote a book about the FAFSA.

First lady Michelle Obama visited T.C. Williams in February to encourage more students to apply.

“Fill out those forms. Fill them out,” she told them. “Almost everyone is eligible for some form of financial aid, and all you have to do to access that aid is fill out this one little form.”

Two months later, guidance counselors orchestrated a follow-up campaign. They set up camp in the cafeteria Wednesday and spent two hours talking to every senior they could find. About 45 percent of T.C. Williams students in the Class of 2014 have filed the FAFSA, according to their records. Ideally, they would like to more than double that number.

Students who filed the FAFSA were rewarded with a sticker and a lollipop. Those who hadn’t found scrutiny and encouragement.

“How do you think you are going to pay for Howard? With your good looks?” guidance counselor Annette Lee said to a 17-year-old senior who was eating a slice of pizza. He told her that he already had a full scholarship. She said he should still apply. “Scholarships don’t always cover books or living expenses,” she said.

Another student told Lee that he was planning to save money all summer before moving to California to enroll in school in the fall. Out-of-state tuition is expensive, Lee said, and it would help to have financial aid.

“You need to make sure your plan is lined up,” she said.

School counselors say there is a pronounced gap between their students’ college aspirations and their reality, which often can be explained by not having a sound financial plan.

More than four out of five graduating seniors in the Class of 2012 at the Alexandria high school said they planned to go to a two- or four-year college. But only 65 percent had enrolled a year later, according to data from the National Student Clearinghouse.

On Wednesday, a third student told Lee that she was headed to Virginia Commonwealth University but that her mom told her the form was complicated and wouldn’t be worth the effort.

Lee agreed that the application was once cumbersome. “You used to need an attorney to help you fill out that form,” she said. “But it’s gotten a lot easier.”

On the other side of the cafeteria, Diana Gomez and Stephanie Reyes said they both filed the form in January, the first week they were able to access it online.

The friends said they hope to be the first in their families to go to college and will need all the help they can get to afford it.

Gomez, 18, received a financial aid package from George Mason University that included three grants, as well subsidized and unsubsidized loans.

Reyes, also 18, said she is still waiting for her aid package from the same school.

She said the application took less than an hour. “It was easy,” she said. “I thought it would be harder.”