It certainly makes sense to identify gaps prior to placement above the level of one's formal instruction history, but given the existence of publisher-provided placement tests in most math curricula, it would likely be more efficient to use those instead of a district-made test with no psychometric anchoring data. Or in the absence of placement tests, the end-of-course exam for the grade to be skipped. Those definitely exist for every commonly available published curriculum, and are highly unlikely to be designed for five-hour administration.
To be fair, it is possible that the district really is not requiring a test that is expected to take five hours. The time listed may be an upper limit intended to allow for extended time. (For example, our state high-stakes test allows for up to five-plus hours for each section--a full school day--but sections are designed to be reasonably completed by an NT student in an hour plus or minus.)
