It is good for the teacher to be kind and gentle towards young and old, but if the situation calls for discipline or a (light) smack that is not severe, that is permissible. It is the habit of the foolish to behave badly and not show any respect, so there is a need for strictness and strength that is more effective than kindness and gentleness. End quote.
Shaykh ‘Abd al-Rahmaan ibn Jibreen (may Allaah preserve him)
Fataawa ‘Ulama’ al-Balad al-Haraam, p. 399
See also the answer to question number 50022
And Allaah knows best.