First of all most rebbes hit when they lose control,
1)It is NOT Discipline if you’re not in control.
2)If you are a Good Mechanech you dont need to get physical.
3)Today there are many inexperienced unqualified rebbes out there.
even if there are some good ones, I can’t give free reins to all
because some can be trusted.
Therefore 100% assur. Rebbes! keep your hands to yourselves!