Our 2030 daughter started playing club volleyball after a few years of church/school league volleyball, where there was typically a HS aged referee and either parents/coaches or other HS age kids called the lines, kept score/book, and everything seemed to go well.
For club in league and tournament play, an idle team from the age group calls the lines, provides the 2nd referee, and keeps the score and book (their coaches assist them). For a bunch of 9/10 years olds, it was impressive how well they did. Very, very rarely did a coach appeal to the first referee on a call, and I don't think ours ever did. I guess they figured the calls would even out over the evening or weekend, and these coaches are from a perennial HS and club volleyball powerhouse. It was also made known to all parents that the 1st referee can and will toss any coach or spectator from the facility for poor behavior, often without issuing a warning (never happened in any of our matches).
It was rather refreshing to simply watch the kids play without anyone getting all over someone. Same holds true at the older ages.
Edit: She still plays church/school league. When that season ends, club picks up.