Using isospin relations, we predict the standard model correlation between Sp0KS=(sin?2ß)p0KS and Ap0KS, the mixing-induced and direct CP asymmetries of B0?p0KS. The calculation uses flavor SU(3) only to fix the isospin-3/2 amplitude through the B±?p±p0 branching ratio, and thus has a small irreducible theoretical error. It can reach percent level precision thanks to expected future lattice-QCD progress for the calculation of the relevant SU(3)-breaking form-factor ratio, and serves as a benchmark for new-physics searches. We obtain an interesting picture in the Ap0KS–Sp0KS plane, where the current experimental data show a discrepancy with the standard model, and comment on the direct CP asymmetries of B0?p-K+ and B+?p0K+. A modified electroweak penguin with a large new CP-violating phase can explain the discrepancy and allows us to accommodate also the corresponding data for other b?s penguin-dominated decays.