It is not about whether the parents could be bothered or not, it is about trying to ensure that their children get the best opportunity possible and if that means having to communicate with the parents in their native language so be it.
If you want to give the children the best opportunity then integrating in the country you live in is a good start, and in my opinion if you still need a translator to speak to a primary school teacher after several years then that's got nothing to do with helping your kids, it's lazy and rude.
Yes and no. My German is good enough after 3,5 year that I can follow Elternabend and a regular Elterngespräch. But if there was a critical meeting coming, I would want to make sure that I understand everything correctly and that I can say the right things. Hasn't happened so far, but it might happen one day, and I know someone who ended up taking her daughter out of private school because of a situation that pribably could have been defused by using a translation, even though both parents speak acceptable German. Something got lost in translation, things were said that shouldn't have, things were understood wrong and birdges were burned. That can also happen after you've been in a country a while.
The way I see it, it also provides a security for the school. That way, nobody can blame the results of the meeting on misunderstandings or crappy translation done by a friend of the parent.
But I agree that using a translator at the Gemeinde's expense when one could get by with crappy German and a bit of goodwill isn't an efficient use of public money. If nothing else, because you need to practice to get better; speaking for myself, most of my progress in German come from speaking to the school (the rest is from the endless email writing to the Vervaltung ). I also get massive goodwill for trying, and somehow I think it reflects on the Troll.
In my experience it's very common for people who've been here for only few years to be less than fluent, for a large number of reasons - only one of which is laziness or rudeness.
The focus of the authorities is, quite rightly, the children's education - not any deficiencies the parents might have. If a teacher speaks better English than the parent does the local language, then it is in the child's interest to communicate with the parents in English. A translator for a few years does, however, seem a bit OTT. But maybe it doesn't come out of taxes - perhaps it's a service manned by public spirited volunteers?
Funnily enough, the only time I've had to have a translator is when I bought a house. But that was for legal reasons. The actual discussions were all conducted in English - buyers, sellers and the officials all perfectly fluent! The translator just sat there...