Each school has unique admission requirements, but, in general, a higher score is always better. There is no real minimum score. This is because the tests are scored normatively and are based only on comparative performance of other students that are applying to the same grade. Thus, the scores schools look at are percentiles and stanines, rather than the absolute number of questions the student gets right or wrong.
For example, if every student that takes the test this year gets 5 out of 10 questions correct but your student gets 6 of 10 correct, then your student will be in the 99th percentile, having done better than every other test taker. So you don't need to worry about getting every question on the test correct.