“Commercial driver training school,” for the purposes of this chapter, means a business enterprise conducted by an individual, association, partnership or corporation for the education and training of individuals, either practically or theoretically, or both, to operate or drive motor vehicles or to prepare an applicant for an examination to be given by the state for an operator's or chauffeur's license or learner's permit, which school makes a charge for such services. This chapter does not apply to any person giving driver training lessons without charge, to employers maintaining driver training courses without charge for their employees only, or to schools or classes conducted by colleges, universities or high schools for regularly enrolled full-time students as part of the normal program of those institutions.