As a former high school history teacher in the South Bronx, I rallied my students with the necessarily optimistic classroom motto of “Anything is possible.”

Just before Christmas, the U.S. Senate effectively told some of my former students, “No, it’s not.”

By voting 55-41 to block advancement of the DREAM Act, the Senate slammed the door shut on thousands of students’ futures and threw away the key for at least another two years.

The Development, Relief and Education for Alien Minors Act would have provided a way for children who were illegally brought to this country by relatives to gain citizenship. The reward — citizenship — was to be dangled as a carrot for children who have been in this country for five years, graduate from high school, pursue college or the military and have no criminal record.

As a teacher and in my current capacity as a college preparation program director, I have worked with several such upstanding students who would have qualified for relief under the act, and it’s crushing to hear them talk about what their futures look like without this legislation.

One of my undocumented former students attends community college — by being ineligible for federal financial aid, his options were very limited — and hopes to someday transfer to a 4-year college to pursue his passion in astrophysics. This student, the former captain of our high school soccer team, has the intelligence and audacity to have had a high-level debate on black holes with Dr. Neil deGrasse Tyson, a Bronx native who currently directs the Hayden Planetarium at the American Museum of Natural History. Without the DREAM Act, though, my former student knows his future includes working on the fringes of society as a doorman, custodian, busboy, or in another little-noticed occupation.

Another of my undocumented former students has the leadership ability and appeal to be elected student body president. However, his parents are so protective of him and afraid for themselves that they bar him from applying for any trips or programs that involve flying, lest the authorities become aware of his status. He recently applied for an alternative spring break project in New Orleans, only to have his parents keep him from turning in the application. One of his fellow undocumented classmates is so fearful of being “found out” that she speaks only when necessary, preferring to blend in and otherwise keep a low-profile.

All of these students are or were fixtures on the school’s honor roll and would like to matriculate to a 4-year college and pursue a career. They have talents to offer society and the promise to make a difference in their community.

But because these students’ families exploited our country’s broken immigration system when they were between 1 and 5 years old, Congress wants to hear nothing of it, and Republican senators are determined to relegate my talented students to society’s margins. In the hubbub around the December vote, many dissenting senators purported to care deeply about these students and would-be citizens. Yet by refusing to pass the DREAM Act until it is included with comprehensive immigration reform, these same senators are using their intransigence to hold students’ lives hostage.

Try as I might, I cannot wrap my head around why support for the DREAM Act and support for comprehensive immigration reform have to be mutually exclusive, as these senators argue. I can understand pursuing and possibly even deporting some illegal immigrants, especially those who break the law again — as the Obama administration has done in record numbers. But Congress’s failure to pass comprehensive immigration reform over the last decade — and the government’s collective failure to secure the border for many decades prior to that — is no reason to hold my students and those like them accountable for their parents’ actions when the students were infants.

Last month’s vote means the DREAM Act is unlikely to move forward until at least 2013, at which point my former students, aspiring astrophysicist and potential politician among them, will likely be nowhere to be found.

Brendan Lowe taught global history at a high school in the South Bronx as a Teach For America corps member. He currently is the director of a college preparation program at a South Bronx high school.