How would you purpose that the not-terrible officers do something about the terrible officers? What should the great and inspiring teachers do about the bad teachers?
There are two unions representing metro train drivers in London, and I have little respect for RMT since they've gone on strike to defend a driver who was sacked for turning up drunk to work[1]. The other union (ASLEF) seems more reasonable.
When an issue is important to both unions (e.g. pay for nighttime services) they wield considerable power. If only RMT strike, there's significant disruption but trains still run.
[1] https://tfl.gov.uk/info-for/media/press-releases/2015/februa... / https://www.theguardian.com/uk-news/2015/mar/07/london-under...