Since the previous Kanji character was one used in student, 学生 (がくせい) it only makes sense to go for the Kanji for teacher 先生 (せんせい) next.
The etymology for this character is that of one person walking ahead of another… I hardly see it, I can find two legs… and well let’s say this one probably changed a bit since it’s conception, it’s that or it needs more imagination than I’m putting in to see it. In any case, the lower half of the radicals can indeed be found on other Kanji.
Anyway, this character is used not only for teacher, but for words like 先(さき), ahead, and 先ず(まず) first, beforehand. The reason for this is that a teacher is someone who logically (or rather, most of the time) came before you, and knows something you don’t know or can do something that you can’t do. It’s also normal to call doctors 先生 (せんせい). The One Piece filler that comes right after Frankie joins, has a kid that calls Chopper 先生 (せんせい) instead of doctor, which is 医者 (いしゃ) by the way.
先 (さき) – 1- previous, prior, former. 2- tip, end. 3- destination. 4- the first priority, future, objective, sequel
先 (さき) の人 (ひと) は 落とした (おとした) さいふ を 探して (さがして) います
The guy from before is looking for the wallet he dropped.
先 (さき) が 丸い (まるい) はさみ
先 (さき) に 立って (たって) 行く (いく)
To go before
先ず (まず) – 1- first of all, to start with, 2- hardly (when used with a negative verb)
先ず (まず) は 公園 (こうえん) を 歩きましょう (あるきましょう), それ から 休んで (やすんで) 話しましょう
First of, let’s take a walk on the park, then we’ll rest and talk.
彼 (かれ) は 先ず (まず) 休みません (やすみません)
He rarely rests.
先生 (せんせい) – Teacher, master, doctor.
私 (わたし) の 日本語 (にほんご) の 先生 (せんせい) は 鈴木 (すずき) さん と言います (いいます)
My Japanese teacher is called Mr. Suzuki.
先生 (せんせい), 頭 (あたま) が 痛い (いたい) です
Doctor, my head aches.
A Kanji with very few readings, but those that are, are diverse!, sometimes multiple uses and meanings, luckily all of them are either logical or natural, so! it makes sense.