primary grades meaning in English

小学低年级。

Of these two primary grades all other grades were varieties .
其它种种级别都是这两种主要级别的异称。
Since research shows that children in the primary grades and minority and low - income children benefit most from smaller classes , it makes sense to direct resources particularly toward these children
由于有研究表明，低年级学生、少数民族学生、来自低收入的家庭的学生从小班中受益最大，因此应优先选择这些学生。