(b) The driver of such school bus, when receiving or discharging passengers who must cross a public highway, street or private road, shall instruct such passengers to cross in front of the bus and the driver thereof shall keep such school bus halted with red signal lights flashing until such passengers have reached the opposite side of such highway, street or private road. Whether such passengers are crossing such highway street or private road or discharging to the same side of such highway, street or private road, the driver of such bus shall keep such school bus halted with red signal lights flashing until such passengers are at least fifteen feet from the bus and either off the highway, street or private road or on a sidewalk.

(c) Every person convicted of a violation of subdivision (a) of this section shall: for a first conviction thereof, be punished by a fine of not less than two hundred fifty dollars nor more than four hundred dollars or by imprisonment for not more than thirty days or by both such fine and imprisonment; for a conviction of a second violation, both of which were committed within a period of three years, such person shall be punished by a fine of not less than six hundred dollars nor more than seven hundred fifty dollars or by imprisonment for not more than one hundred eighty days or by both such fine and imprisonment; upon a conviction of a third or subsequent violation, all of which were committed within a period of three years, such person shall be punished by a fine of not less than seven hundred fifty dollars nor more than one thousand dollars or by imprisonment for not more than one hundred eighty days or by both such fine and imprisonment.

(d) For the purposes of this section, the term "passengers" shall mean those persons designated in paragraph (d) of subdivision twenty of section three hundred seventy-five of this chapter.