Question

students and their teachers are usually in school for 240 days year什么意思

Answer 1

学生和他们的老师通常在学校一年待240天。

重点词汇：
student 英[ˈstju:dnt] 美[ˈstu:dnt]
n. 中学生; 学生，大学生; 研究者，学者; <美俚>初学者;
[例句]Warren's eldest son is an art student, at St Martin's.
沃伦的大儿子是圣马丁学院艺术系的学生。

teacher 英[ˈti:tʃə(r)] 美[ˈtitʃɚ]
n. 教师，教员，老师，先生; [航] 教练机;
[例句]I'm a teacher with 21 years 'experience.
我是个有21年教龄的教师。

usually 英[ˈju:ʒuəli] 美[ˈjuːʒuəli]
adv. 通常，经常，平常，惯常地; 一直，向来; 动不动，一般; 素;
[例句]The best information about hotels usually comes from friends and acquaintances who have been there.
关于酒店的最可靠信息通常来自曾经去过那里的朋友和熟人。

year 英[jɪə(r)] 美[jɪr]
n. 年; 年纪; 一年的期间; 某年级的学生;
[例句]The year was 1840.
那是1840年。

Answer 2

Students and their teachers are usually in school for 240 days year
翻译：学生和老师经常一年240天都在学校（说明师生工作学习时间长，压力大）
原句中in school 最好要改成at school或in the school，后面的year前面要加a，即Students and their teachers are usually in the school for 240 days a year。

Answer 3

Students and their teachers are usually in school for 240 days （a/every）year.
学生和老师通常一年/每年有240天在学校。
分析：目测year前面丢了一个词，补充后可译为上文。