That's our teachers nowadays...Teachers will not explain. That's why I still review the homework my kid does and explain to him whenever I spot a mistake. I tried to raise to teachers for some uncertainties. Seems like they follow the "rule book"!!! or just the sample compositions to determine whether or not your kids will get good result, But teachers did not say so during the classes.
Like you said, kids don;'t have time to do reading...though it's a very effective way to improve your reading and writing skiils. But really, no time at all. And even no time to look for the meaning or sample sentences from the dictationary...