Short answer: A policy being race-neutral does not preclude it from being racist.
Long answer: A race-neutral policy is one that does not take race directly into account. And yes, the SHSAT exam is race-neutral. Also, for a long time now our courts have strongly preferred race-neutral approaches to diversity through a long list of rulings.
A race-neutral approach to diversity typically uses a race proxy to diversify its student population. E.g. recently, the state of Connecticut switch from race quotas to considering a myriad of non-racial student attributes for admissions. Attributes such as family-income and other socio-income factors. The effects of these new race-neutral admissions criteria are expected to be the very similar to race-quotas.
It stands to reason that if we can use race-neutral policies to increase diversity, that we can also use different race-neutral policies to DECREASE diversity.
The trick in both cases is to find an effective race proxy. In the SHSAT Exam's case, the proxy is exposure to high-quality exam specific preparation. Whether that prep is available at school, at home or through a third party for thousands of dollars per month.
But it's also important to remember that exam-specific prep ( aka "teaching to the test" ) does not improve the student's academic ability, which is what is supposed to be predicted with the SHSAT. In the end, the Black and Latino students left behind are often 1-2 multiple-choice questions lagging behind the prepped students.