Section 54. Every school physician shall make a prompt examination of all children referred to him as provided in this chapter, and such further examination of teachers, janitors and school buildings as in his opinion the protection of the health of the pupils may require. Every such physician who is assigned to perform the duty of examining children who apply for health certificates shall make a prompt examination of every child who wishes to obtain an employment permit, as provided in section eighty-seven of chapter one hundred and forty-nine, and who presents to said physician the pledge or promise of the employer, as provided in said section; and the physician shall certify in writing whether or not in his opinion such child is in sufficiently sound health and physically able to perform the work described in said pledge or promise.