[SavageBoys]

Mahou Sensei Negima? 2003-2012, fully complete. Even has a continuation called "UQ Holder!" which is currently ongoing.

Plenty of chapters to burn through (355+), anime isn't worth watching unfortunately.

Fits all your desired genre tags with a bit of a caveat.. the MC is the teacher not the student.

Id say the art style is pretty great for its time:
Spoiler (Click to View)

[bluetile]

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