After months of waiting, all public and private schools in San Diego County received the green light to reopen for instruction starting Wednesday, now that the county’s COVID case rate has finally stayed low enough to reach the state’s less-restrictive red tier. The momentous yet expected tier announcement by county officials Tuesday, along with a decision by a county judge on Monday, cleared the way for an expanded reopening at some North County districts that have for weeks been asking the state to reopen their middle and high schools. At least three of those districts — Poway Unified, Carlsbad Unified and San Dieguito Union High — this week started offering at least one day a week of in-person instruction to their middle and high school students.