Parents of special needs students probably need these more than anyone. Their student might need a sixth grade language program but a second grade math program. Once your child starts in a certain program and finds a level that is good for them, then a home school placement test is usually not necessary anymore because you can just buy the next book in the series when they finish one. When switching books or curriculum, finding the right level can be a little more tricky.
Sometimes a Learning Style Assessment can be even more helpful to a parent than a placement test because the parent finds out how their student learns best. If their child is a hands on learner, getting the right level workbook still might not be what this child needs to develop a love for learning and be able to remember what they learned.
The page I have written includes all the placement tests I have found along with a discount link to a Learning Style Assessment that you can do with your child. I hope these are all helpful.
Home School Placement Test