日本の 小学校では、六月に プール開きが あります。
水泳の 練習が 始まると、学校中が にぎやかに なります。
子どもたちは 安全な 泳ぎ方や、水の 中での きまりを 習います。
Why six school grades, and not N5–N1?
Because that is how Japanese children learn to read. Japan's Ministry of Education fixes exactly which character belongs to which grade — so "grade 3" is a boundary you can verify, not a feeling. Every article here is machine-checked: if a single character sits above its grade, it is not published.
The result: you never hit a character you have not learned. That is the whole reason this product exists.