"二年级学生的" can be translated into English as "for second-grade students" or "of second-grade students", depending on the context.
If you're referring to something specifically designed for or intended for second-grade students, you might say "for second-grade students" (e.g., "a textbook for second-grade students").
If you're describing a characteristic or property that belongs to second-grade students, you might say "of second-grade students" (e.g., "the abilities of second-grade students").
In many cases, especially when modifying a noun, the prepositional phrase "for second-grade students" is more commonly used.