The large majority of the testing gap is not explained by test prep courses. Most of what is impacted by that test prep is on the upper end of the spectrum anyway. If test prep-specific courses were exactly equal the overall issue would still be very similar. There's a reason high-performing schools don't devote hardly any classroom time to test prep.
And focusing on test prep is also a huge problem when it discourages most low-performing students and even many high-performing students from the learning process (because it's generally boring as fukk) and diverts a huge amount of potential learning time from productive activity into pure system-gaming bullshyt.
