"Teaching of children is important."
Translation:Undervisning af børn er vigtigt.
It's been explained to me in the meantime, elsewhere on DL. It's do with 'undervisning' being a very general abstract thing in this sentence. It remains an '-en word', but takes a neutral adjective. If the sentence were about a particular instance of undervisning, something like 'Sophie's teaching of maths is good', say, the adjective would be without the t: 'god', not 'gott'. (Native speakers, please let me know if my explanation is imperfect.)