No district shall classify its pupils with reference to race, color, social position, or nationality, nor separate its pupils into different schools or departments upon any of such grounds. Any district so classifying or separating any of its pupils, or denying school privileges to any of its pupils upon any such ground shall forfeit its share in all apportioned school funds for any apportionment period in which such classification, separation, or exclusion shall occur or continue. The state commissioner upon notice to the offending district and upon proof of the violation of the provisions of this section, shall withhold in the semiannual apportionment the share of such district and the county auditor shall thereupon exclude such district from the apportionment for such period.