Shii-Sensei in the Mountains

       ┏━━━━━━━━━━━━━━━━━━━━━━━━━━┓
       ┃┌────────────────────────┐┃
       ┃│.  ! ////////// └┘ \\\\\\\\. │┃
       ┃│.  ! /////////          \\\\\\\. │┃
       ┃│゙‐┴─┐ ̄ ̄ ̄ ̄ ̄ ̄             ̄ ̄ ̄ ̄~┌─ │┃
       ┃│ ‐ ─┐|                               │   │┃
       ┃│.  北 |├┐田  田  田  田  田  田  田 ┌┤   │┃
       ┃│   モ |├┤                           ├┤   │┃
       ┃│   ラ│|::│                           ││   │┃
       ┃│第 ラ│|::│           ___          ││   │┃
       ┃│.3 小 |││.田  田  田  |    ゙| 田  田. .││   │┃
       ┃│分 学.|,,,_∧              ∧ ∧  |   ∧_∧.゙││   │┃
       ┃│校 校.(#゚;;-゚)  .∧_∧     (*゚ー゚)  .|∧_∧ ´∀`) ∧∧.  │┃
       ┃│── U;; ;;∧∧( ・∀・)∧,∧(|  .∧∧ ´∀`)ヽV/,)=゚ω゚) . │┃
       ┃│:   ~|;; ;;(*゚∀゚)っ   ミ,,゚Д゚ミ.!   (*゚ー゚)つと) |  |([.  |:|. ゙│┃
       ┃│;;, . .   U !.(_,,). U !.@ミ,,,,,,,,,ミ U U(,,uu) U U__)__)ノ__,|:ゝ:: │┃
       ┃│""''''"''''                             '"''│┃
       ┃└────────────────────────┘┃
       ┗━━━━━━━━━━━━━━━━━━━━━━━━━━┛

Shii-Sensei in the Mountains (山奥のしぃ先生) was a popular thread/long story about Shii becoming a teacher at an elementary school deep in the mountains. The story was started by ◆O4iuhEB.DQ氏 aka. "His Excellency Yamaoku", but many different posters added onto it.

Sources: