It’s not a good idea, in my opinion, to demand grammatical accuracy from language learners in school, because so few of them end up speaking the language. What does it matter whether they are able to nail niceties of grammar at the age of 12? To me, it doesn’t matter. If there’s some way of making them enjoy the process of language learning so that they expose themselves to the language, they develop some degree of comprehension, they develop a certain level of vocabulary, that’s good enough.