[文法] 請問此句中的at跟in的用法

[zentak (BG HANCHUN)]

   各位好，曾在空中英語教室中看到以下的文章:

    He received his education at the Taiwan Central Police College.
    At age 22,he became the youngest captain ever in the Taipei Police
    Department.

    一樣是場所，請問為什麼Taiwan Central Police College用at，而Taipei Police
    Department用in呢??

    煩請各位解惑，謝謝!!

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→ jacqueswu:也許警察學院規模比台北警察局小吧?
→ hansi:我的想法是school >> physically exists
→ hansi:Police Department >> abstract/conceptual idea
→ hansi: 所以整個Police Department 涵蓋範圍就比學校大很多, 2c
→ PUTOUCHANG:應該與範圍無關
→ PUTOUCHANG:at college 側重"學習", ex: learn skills at college
→ PUTOUCHANG:in college 稍微不同, ex: my old friends in college
→ PUTOUCHANG:不過我也沒辦法清楚地說明... 感覺上有差
→ PUTOUCHANG:in ... department 在...部門裡
→ koalabear:以前我有問過同樣問題，at代表已經從學校畢業
→ koalabear:in 代表他現在正在這個單位服務。假設我說：
→ koalabear:I was a student at the Taiwan Central Police College
→ koalabear:I'm a student in the Taiwan Central Police College.
→ koalabear:第一句是說我以前是警察學校的學生，第二句是我現在是
→ koalabear:是警察學校的學生。這是當時老師回答我的答案，希望我沒
→ koalabear:記錯@@"
→ zentak:謝謝各位的回答，感恩!!