"Brothers and sisters: Be kind to one another" (Ephesians 4:32)
When I was in school, we had teachers and coaches that let us do whatever we wanted. We liked it, but we didn't respect them.
When I was in high school, we had teachers and coaches that yelled at us a lot, and it came from a place of anger and rage. We didn't respect them either.
We also had teachers and coaches who praised the things in us that deserved praise and called us and challenged us to be better in those areas that needed correction. And even in their discipline, I certainly look back on what they did for us, and I would describe their words as "love" and "kindness".
May we be kind in all things, and not simply think that kindness only = smiling