The notion that SAT scores are a poor proxy for IQ in low income households is a commonly held talking point, but it’s just not borne out by research.

Testing prep just doesn’t matter in aggregate, because admissions rarely have a cliff between marginal score and slightly better marginal score. Upper middle class people spending money on it doesn’t mean it’s money well spent; like many things rich people spend money on, it’s largely signaling to peers.

Also, your caricature of why people get hired for engineering jobs bears very little relationship to what I and my colleagues look for in engineering interviews.

Being able to solve a few simple algorithm problems is table stakes. Being able to talk about what you’re doing and why is what’s being measured.

People who crammed leetcode but don’t actually understand the material are obvious 5 minutes into the interview; people who freeze up occasionally on the algorithm bits but can talk about why they’re doing what they’re doing generally get hired.