Inability to cover non-tuition costs and undermatching means that free college widens the education gap.

For one, the plan is badly targeted. Covering the full tuition of all community college students would mean middle-income, and even upper-income, students would get hefty subsidies, even though many do not need the help. Meanwhile, many lower-income students at community colleges would still not have the money to cover the non-tuition costs, such as books, supplies and transportation – and room and board for those not living at home. These costs usually dwarf tuition at a public community college – annual total costs averages over $16,000, while free tuition would account for only about one-fifth of that. True, lower-income students can qualify for Pell grants, but the maximum this year is $5,730, making community college a financial challenge for many, even if tuition were free.

Rather than spend $60 billion to make tuition free to rich and poor alike, a better approach would be to apply an income test and make any new federal program a sliding-scale contribution to total costs.

What’s more, community college is usually a dead end.Rather than being a firm first rung on the higher education ladder, for too many, community college turns out to be a broken rung. Just 20% of students who begin a two-year public community college program actually graduate within 3 years, and typically only 60% of enrolled students return the following year. As for being a low-cost gateway to a successful four-year college, just 15% of students entering community colleges earn a bachelor’s degree within 6 years.

So rather than putting so many eggs in the flimsy community college basket, it would be wiser to help states and school districts provide a fuller range of opportunities at the high school and college levels, such as professional credentials, apprenticeships and high-school career academies.

The plan could also add to the undermatching problem. A grave concern about higher education in America is that many high-performing high-schoolers, especially from less-affluent African-American and Hispanic households, do not apply for challenging universities for which they actually have the academic ability. Instead, many such young people settle for community college or less rigorous four-year institutions. This is a phenomenon known as “undermatching.” This happens for several reasons, including concerns about the financial risks to the student and his or her family. Undermatching widens the education gap between racial groups, and between richer and less-affluent families.

An unintended consequence of providing free tuition at only community colleges is that it would likely add to undermatching. That’s because many smart high-schoolers who come from minority or less-affluent families, or who are the first in their family to go to college, would for financial reasons be even more likely to opt for community college rather that a rigorous four-year college.

If President Obama can convince Congress to provide funds for a college proposal, a better approach would be to enhance income-based Pell Grant funding for the full range of higher education options, rather than trying to steer students to community colleges.