日本語指導にはステップ（レベル）がありますが、「教科」で日本語を教えることが大切です。
国語・社会・算数・理科など、子どもたちは様々な教科の授業を日々受けます。
日常生活では使わないような単語もあれば、日常的に使う言葉や文法型も多くあります。
日々の授業理解を更に深めたり、授業で活躍できるように、
「実際の授業の単元を教える中で日常の日本語と学習日本語の両方を効率よく教える」
方法は、担任の先生と子ども両方にとって、良いことだと思います。

There are steps (levels) in teaching Japanese, but it's really important to teach Japanese in "the subjects".
Students take classes in various subjects such as Japanese, social studies, math, and science every day.
There are many words that they don't use in our daily lives, and many words and grammatical types that they use in our daily lives.
It's really good for both homeroom teachers and students to teach Japanese in the subjects because it's really efficient and effective. Besides, students can be more active and understand more ;)