As a condition to employment, every public school employee, including without limitation teachers, cafeteria workers, janitors and bus drivers, shall submit a certificate signed by a licensed physician, or by a registered nurse licensed pursuant to Article 2 (§ 54.1-3016 et seq.) of Chapter 30 of Title 54.1, stating that such employee appears free of communicable tuberculosis. Such certificate shall be based on recorded results of such skin tests, X-rays and other examinations, singly or in combination, as are deemed necessary by a licensed physician that have been performed within the twelve months’ period immediately preceding submission of the certificate. After consulting with the local health director, any school board may require the submission of such certificates annually, or at such intervals as it deems appropriate, as a condition to continued employment.