We present static electric dipole polarizabilitiesαd(Z, N) from numerical nonrelativistic re-stricted Hartree-Fock (RHF) finite-field calculations for high-spin open-shell S states (L=0)ofatomsandisoelectronic ions withN≤55 electrons. All these S states result from one or more half-filled shells. Foreight isoelectronic sequences, those withN= 3, 7, 11, 15, 23, 29, 33 or 41 electrons where the electronicground state of the neutral or nearly neutral members is conserved upon increase of the nuclear chargenumberZ, polarizability data are given for ions with charge numberQ=Z−Nup toQ= 90. In ad-dition, these data are represented in terms of rational functions ofQ(with absolute value of the relativeerror of the fit always below 4%). The rational functions are comparable to the classical nonrelativisticresultαd(Z,1) = 4.5/Z4=4.5/(Q+1)4for the polarizability of the2S ground state of a hydrogen-likesystem. Our results also contribute to constitute a reference database (i) for algebraic approaches relyingon basis functions, and (ii) for the discussion of relativistic and correlation effects on polarizabilities alongisoelectronic sequences.