There are "colleges" that are literally just fronts for student visas. Canada just uncovered 10,000 fake student visas; the Australian government recently closed 150 colleges that don't even actually exist.

All of these 'students' are now illegally in these countries, and realistically most will not be caught and deported. Perhaps the worst part is that even at the scale of this fraud, it pales in comparison to the mind-boggling number of students being legally permitted entry to these countries, most of them from India.