I think it's important for children to be interested at learning languages during their study. If it's interesting for you, you will be more motivated, it will be easier and funnier to learn. In my opinion, lessons for children should be short and funny. I'm sure that children memorize emotions connected with there lessons. And if it was boring or terrible for them, they wouldn't have any desire to go again. When I was 8, we started learning English at school. For me it was so boring! I hated this subject. It was really difficult for me. But now it's my favorite subject :) Another example. My brother is 8 years old. He loves playing with his cars, reading and watching cartoons. He likes watching cartoons about Peppa pig. For him it's fascinating. He wants to watch it again and again. And also there is his student book. But I know for him it's a bit boring, so he can't sit and learn English with this book more than 20-30 minutes. But I found a solution: after learning English with his student book (it takes about 15 minutes), he watches one cartoon about Peppa pig. And now he likes his English lessons!