The episode described is not at all uncommon, and extends to players in warmups standing on the sideline. However, I will say that I have been told there is no official technical area in SCHSL soccer, so this is up to a ref's discretion.
Were I king, I'd put in 4 housekeeping rules:
1) Both teams on the same sideline.
2) Limited technical area, for coaching only.
3) Only one coach standing (in technical area at a time).
4) All personnel on sidelines in pinnies or street clothes.
(I'm not holding my breath.)
