The department of education shall consist of the county school board, the division superintendent of schools and the officers and employees thereof. Except as herein otherwise provided, the county school board and the division superintendent of schools shall exercise all the powers conferred and perform all the duties imposed upon them by general law. Except for the initial elected board which shall consist of five members, the county school board shall be composed of not less than three nor more than nine members; however, there shall be at least one school board member elected from each of the county’s magisterial or election districts. The members shall be elected by popular vote from election districts coterminous with the election districts for the board of county supervisors. The exact number of members shall be determined by the board of county supervisors. Elections of school board members shall be held to coincide with the elections of members of the board of county supervisors at the regular general election in November. The terms of office for the county school board members shall be the same as the terms of the members of the board of county supervisors and shall commence on January 1 following their election. A vacancy in the office of school board member shall be filled pursuant to §§ 24.2-226 and 24.2-228. In order to have their names placed on the ballot, all candidates shall be nominated only by petition as provided by general law pursuant to § 24.2-506. The county school board may also have a position of tie breaker for the purpose of casting the deciding vote in cases of tie votes of the school board as provided in § 22.1-75. The position of tie breaker, if any, shall be held by a qualified voter who is a resident of the county and who shall be elected in the same manner and for the same length of term as the members of the school board and at a general election at which members of the school board are elected. A vacancy in the position of tie breaker shall be filled pursuant to §§ 24.2-226 and 24.2-228. The chairman of the county school board, for the purpose of appearing before the board of county supervisors, shall be considered head of this department, unless some other person in the department shall be designated by the school board for such purpose.