Children tend to respond favourably to fairness so a fair system of punishments would, in my opinion, tend to cause a general improvement in behaviour. Individualised punishments might be the most effective for the individual when applied in isolation but their effectiveness would be significantly reduced, or even nullified, if they’re perceived as being unfair when compared to those received by others. The bottled up resentment of an unfair system would, itself, produce a general deterioration in behaviour and, when the lid finally blows, you have real problems.
whole class punishment is bad but not so bad as choosing one victim to punish for something he/she didn’t do.
The resentment in this case will be (in my opinion and with self experience) much worse.