The law already has the exception for you to "reasonably" know where a school is. If you reasonably can not know, then a jury should not convict you unless the prosecution has "beyond a reasonable doubt" has the jury convinced you should have "reasonably" known (e.g. big bright "school crossing signs")
If the prosecution can convince past the "reasonable" exception of the law, then ignorance due to software can be equally (or moreso) argued against; even if you made a "half hearted attempt" (prosecutions words) to comply shows you should know the law AND you didn't put forth the due diligence required to comply.
E.g. It's reasonable for a person to do a complete and full job which would include the mapping of ALL the schools in the area IF one or more of the schools have been mapped (or your reliance upon those schools is demonstratable).
E.g. A reasonable person would know if there are schools in the area, according to the mapping software, then maps and software and data sources do get out dated, hence you should have done more due diligence in order to ascertain where all these schools are.
No, I'm not opposed to knowing where the schools are, in an attempt to ward off a confrontation with the police. I am opposed to showing that you made an effort to comply with the law when that effort may be used against you and the language of the statute is a much better defense.
However, I'm willing to be wrong. Can someone show me some case where the defendant was "trying to comply with the law" and got off because of it?
PS. I drive to California along Pioneer Trail in South Lake Tahoe. There's an elementary school along the side and by basica eyeballing it, I can "reasonably" be expected to know there's a school there. Howver, anything past or off the trail - I don't expect (or try) to know. If the prosecution wanted to try and make a case that I "should" have known of schools closer to the lake - that's their case to try and make. I won't help them by having a map of the area nor 8/10 of the schools mapped out. Hell, it could get scary if you have rifles and circles around schools as they'd call you out as a lunatic threat to the children and you should be locked up.