That's what can be inferred from his column calling for an end to tenure for public school teachers. Job security is part of the pay package for public school teachers. If they can expect less job security, it effectively amounts to a cut in pay. This would be expected to make teaching a less attractive career path compared with the alternative choices.
As a practical matter, there are few (if any) school districts that do not have provisions that allow even tenured teachers to be fired if they are not competent. This may not happen in many cases because their principals are too lazy to document the incompetence, or the higher ups in the school district don't provide them the resources they would need to ensure that classes are being well-taught. These latter problems will not be addressed by the ending of tenure.