Agree with previous posters that there are probably too many variables to make this useful, but I can share where my two are.
Their middle school band teachers require 120 minutes/week, and prefer that it is divided somewhat evenly (ie, not crammed into one or two sessions).
DS 12 has been playing his current instrument for 2 yrs, he practices 20-30 minutes, 6-7x/week.
Dd 14 has been on the current instrument 4 years, she practices for 45min-1hour probably 3-4x/week. She is more of a slacker, and is very good at sight reading, so sometimes slides by; however, her private teacher is quite demanding so this is becoming harder for her to pull off.
This definitely varies depending on schedule constraints, if an audition or performance is coming up, etc. Both take lessons during school and private lessons after school. The practice time is also limited by endurance, both play wind instruments and stamina is a factor.
Regarding outside ensembles, I would say it depends if their needs are met in school. Our school has pretty high-level music, and both kids play in small group ensembles in addition to band. Dd has definitely outgrown what is available in middle school and has auditioned for an been accepted to the highest level band for high school next year. Still, she is going to audition for an outside youth orchestra. This group is the main outside ensemble locally that would be suitable, but you have to be a ninth grader, so she has been waiting patiently to audition. The main reason she wants to try the outside group is that her high school group, though it plays sometimes with an orchestra, is primarily a wind ensemble, and she wants the orchestral experience.
Just to note, in our area there seem to be more opportunities for string players, in terms of outside ensembles, and they start at younger ages, often 6th grade. Our band program doesn't begin until 5th grade, so that may be part of the reason for fewer opportunities there; by then many of the kids have already become entrenched in orchestra and string music.
