Ⅰ. at school表示“在學校、在上學”相對于在家里或在校外。如：

　　① My son is at school now. He is not at home or somewhere else. 我兒子現在在學校，他不在家，也不在別的地方。

　　② When my brother was at school, he studied very hard. 在學校時，我兄弟學習很用功。

　　Ⅱ. in school “在求學、在上學”相對于有工作。如：

　　My daughter still in school She doesn’t work.。 我女兒還在上學，她不在工作。

　　：①和②用at school 強調所在場所或時間。③中的in school 則強調主語的身份是學生。因此，in school. 和 at school的著重點不一樣，通常不互換使用。

　　Ⅲ. In a / the school “在學校”，不一定指上學。類似的還有：

　　in hospital “生病住院”

　　in a / the hospital表“在醫院”(工作或探視病人等)

　　at table “在吃飯”

　　at a / the table “在桌邊”(有可能在聊天或看報)

　　① Is your friend in school? 你的朋友在上學嗎?

　　① Your friend looked for you in the school just now. 剛才你的朋友在學校里找你。

　　② Children are often in hospital when they are young. 孩子們小的時候經常生病住院。

　　③ She is a good doctor in the hospital .她是醫院里的一名好大夫。

　　Ⅰ. at school表示“在學校、在上學”相對于在家里或在校外。如：

　　① My son is at school now. He is not at home or somewhere else. 我兒子現在在學校，他不在家，也不在別的地方。

　　② When my brother was at school, he studied very hard. 在學校時，我兄弟學習很用功。

　　Ⅱ. in school “在求學、在上學”相對于有工作。如：

　　My daughter still in school She doesn’t work.。 我女兒還在上學，她不在工作。

　　：①和②用at school 強調所在場所或時間。③中的in school 則強調主語的身份是學生。因此，in school. 和 at school的著重點不一樣，通常不互換使用。

　　Ⅲ. In a / the school “在學校”，不一定指上學。類似的還有：

　　in hospital “生病住院”

　　in a / the hospital表“在醫院”(工作或探視病人等)

　　at table “在吃飯”

　　at a / the table “在桌邊”(有可能在聊天或看報)

　　① Is your friend in school? 你的朋友在上學嗎?

　　① Your friend looked for you in the school just now. 剛才你的朋友在學校里找你。

　　② Children are often in hospital when they are young. 孩子們小的時候經常生病住院。

　　③ She is a good doctor in the hospital .她是醫院里的一名好大夫。