I agree however anything in a school-zone when kids are getting picked up (private or public school) is always going to get a cops full attention deserved or not ... this is just common sense.
School zones are pretty much "zero tolerance" zones for any moving violation. (as it should be!)
Cops should enforce traffic safety in schools zones, true, but the use of an arrest is not something that should be done by government just because the person "deserves it" based on ethical grounds or mere potential threat to life. The potential arrested party could very well suffer certain damages that he also has a right to recover if the facts justify such a case. If for example, a income earner whose job demands reporting to work daily "or else" is stuck in jail for a day or two and his work was not done, he has grounds for a lawsuit against the police department for lost wages. The vehicle he was driving may have also been impounded and a fee required for release, and there is potential stolen property by the impounder.
The legal system is very much a system, and thus whatever basis a rule used to enforce a law can have a legacy "in the future" that goes well beyond the intended "fix". In the U.S, law enforcement very much was aggressive in arresting over the smallest of things in the past; this wound up allowing civil rights movement lawyers to start a chain of appeals that landed in the Supreme Court and basically made a significant change to the law of the land. Possibly in response, the "non-incarcerable" offense got cooked up, and that basically is a way for the state to enforce laws without the risk of an chain of appeals that can be started. Without the threat of incarceration, there is no "right to counsel" or a public defender.
It's not just criminal law that used to have the of incarceration. Some code enforcement locales used to employ the penalty of criminal incarceration for non-compliance, including San Francisco. Camara vs. San Francisco was a case in which Camara denied entry of a code inspector into his facility, and got some jailing.
Also, from an "economic or bottom line" perspective, the cop would rather fine because it's less costly even without a threat of a lawsuit. He doesn't even have to show up in court for certain violations. It's better for "profit" to just fine and warn.
The points brought up by MtnMan can be summarized generally
1. The degree of actual material harm.
2. The safety issue of having a huge backlog of private vehicles, not schools buses,
3. The behavior of the driver was not reckless or aggressive
While none of these points can contradict a violation of law occurred or that the potential of harming a someone was created, they do
1. bring to light another matter of safety or cost to "society" due to inadequate vehicular space on private property(space to park) or the road itself(a second lane) to accommodate the number of cars at the time
2. the degree that the driver should be penalized.
In my locale, there is a car wash near a main throughfare. At some point, a notice by police showed up that the cars waiting in line for service may not spill over onto the main street.