Sen. Chuck Grassley, R-Iowa, is confronting the Department of Homeland Security about a special program under which groups "pose as education institutions in order to secure visas for tuition-paying foreign students."

The students, the senator points out, are then able to obtain three-year work permits and are exempted from payroll-tax requirements.

"Visa mills are those marginal educational institutions that provide visas and work permits to foreign students, but little in the way of actual schooling," explains the Center for Immigration Studies.

The work permits under the Optional Practical Training program "actually give the alien students' employers a tax break for hiring them instead of comparable citizen and green card students."

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Grassley, in a letter with pages of questions posed to DHS, pointed out that the foreign students are given three-year work visas, even if they aren't offered any reasonable education.

"These 'visa mills' profit from the foreign student tuition and face little governmental oversight when issuing work visas under the program, which is not available to American students," the senator explained.

"Employers also benefit from hiring foreign student over American workers, as neither the employer nor the foreign students is required to pay payroll taxes for the work," he said.

Grassley said that with all of the financial incentives granted the students, schools and employers, it's not surprising "that foreign student enrollment has exploded, while recent American grads are un- or under-employed."

"Unfortunately, our government has delegated much of the authority surrounding foreign student employment to the very individuals and entities that benefit the most, schools and school officials," he said.

David North at the Center for Immigration Studies noted, "To my knowledge, this is the first time that DHS has been asked by Congress about visa mills and OPT; one hopes that it will stir some interest in DHS about issues long neglected by that agency."

He previously noted action taken against a visa mill that that had been described in India as "an academic rip-off."

Grassley said foreign students "contribute to a growing population of non-immigrants who overstay their visas."

"In 2016, more than 79,000 foreign students overstayed their visas – an overstay rate nearly three times greater than that of the general non-immigrant visa population."

He pointed out that many reputable colleges enroll foreign students, but there are others.

"These institutions, many of which operate as section 501(c)(3) (tax-exempt) educational institutions, are costing American workers millions of dollars in lost taxes and employment opportunities, and contribute disproportionately to the large and growing population of foreign students and exchange visitors – nearly 80,000 in 2016 – who overstay visas to remain in the United States without legal authorization."

It's also a national security concern, he said.

There were more than a quarter-million "foreign students working in one of these government-approved, alien-only, paid 'training' programs, as of August 2017," he noted.

Students are drawn by the money, and schools want to maximum revenue. To do that, he explained, schools such as Pomona College, Williams College, Yale and MIT "all recently reclassified their economics programs so that they qualify for the Department of Education's 'STEM' designation, because foreign students in STEM fields can work in the U.S. for three years or more after graduation."

U.S. employers also cash in because they are exempted from payroll taxes for the workers.

Grassley said the problem is huge.

"Tri-Valley University (TVU), was certified to admit 30 foreign students in 2009 but by May 2010 – when ICE began an investigation – had enrolled 939. The next fall, Tri-Valley had 1,555 foreign students, before the school was shuttered due to an astonishing list of criminal activity by the school's founder, Susan Su. TVU 'students' reportedly took no classes, but exchanged tuition and fees for I-20s and work approval. After closure, hundreds of TVU students were, mystifyingly, permitted to transfer to other schools."

Grassley is asking DHS how the work permits are monitored, who looks at students' training plans, how problems are corrected and more.