In any county to which Section 6-5 applies and which has 100,000 or more inhabitants, no person may serve on the board of review who has not passed an examination prepared and administered by the Department to determine his or her competence to hold the office. The examination shall be conducted by the Department at some convenient location in the county. The Department may provide by rule the maximum time that the name of a person who has passed the examination will be included on a list of persons eligible for appointment or election. The county board of any other county may, by resolution, impose a like requirement in its county. In counties with less than 100,000 inhabitants, the members of the board of review shall within one year of taking office successfully complete a basic course in assessment practice approved by the Department. In counties with 3,000,000 or more inhabitants, the members of the board of review shall successfully complete a basic course in assessment practice, approved by the Department, within one year after taking office.