purchase by grade

例句：

1. 1. The school offers a variety of courses for students to purchase by grade.
   学校为学生提供多种课程，学生可以按年级购买。
2. 2. The parents decided to purchase the latest model car for their child, but they wanted to wait until hereached the appropriate age.
   家长们决定为孩子买最新型号的汽车，但他们想等到孩子达到适当的年龄再买。
3. 3. The company has introduced a new product line that is sold by grade, making it easier for customers to find the right one for them.
   公司推出了一个新的产品线，按年级销售，这使得顾客更容易找到适合他们的产品。