25% of the population without a secondary education diploma looks pretty bad to me. To me it looks like a positive that that number has been increasing in the last 2 decades. For comparison: the EU target is 9% and the average across the EU countries is now 9.5%.

I wouldn't try to link those SAT scores to graduation numbers. Graduation numbers will be for both vocational and academic schooling, while the SAT scores are only relevant for the academic route.