Here is an overview of the practice of "gateway testing", which explains it much better than I could:
But for completeness I'll quote the basic idea:
What’s a gateway test? Our definition is that it is a test of basic skills. These may be skills that are prerequisite for success in a course, or may be skills which every student in a course should develop.... However, while these skills are intrinsic to or essential for success in the courses, they are not our educational focus. Our courses focus on conceptual understanding... Our gateway tests are 7 or 10 question tests, administered on-line... which students may take multiple times and which they must complete with almost no errors to pass.... Students may practice the tests as many times as they like, but to get credit for having passed the test they must take the test in a proctored lab where their identity is verified and where they are not allowed to use outside resources.... completion of the test is not a part of the students’ course averages; instead, any student who doesn’t pass a gateway by the specified deadline... has her/his final grade reduced by 1/3 to a full letter grade at the end of the semester.
The above link includes a bit of evidence that the gateway tests work at Michigan, at least that they correlate with students learning the gateway material. But I would like to know if any more serious data analysis has been done on gateway tests (anywhere)? In particular, I would like to know whether implementing gateway tests has a positive effect on overall student performance.