This question has come up several times over the past months/years. And I have given my opinion(s) - however I recently did a little more research to see what colleges and universities are requiring for their incoming horn student auditions.

The minimum I found was major scales in two octaves up to 5 sharps and 5 flats at quarter note equals 100bpm.

More commonly what I found was major scales in 3 octaves, quarter note= 100 - 144bmp. High end of range to be at least Bb (2 spaces above the trebel clef), low range to be at least Bb (second line bass clef).
AND the ability to transpose in A, D, and C.

I hope this helps prepare those who wish to continue into and through college as a horn player.