Hello @skiger
It sounds like the Ethernet connection to the sanctuary unit may not be managing to negotiate the 1Gbps speed and is falling back to 100Mbps speeds. I would investigate that wire, perhaps using a laptop connected to it to test. Once that wired connection is reliably maintaining a 1Gbps speed, the WiFi unit connected to it should be able to deliver similar speeds as from the office. Just to verify, though, make sure it's wired into the LAN Ethernet port on the office (primary) access point, too (not to any "outer" network the office access point's WAN / globe Ethernet port is connected to).
Do be aware that when a secondary access point (like your sanctuary unit) is wired back to the primary, it can't carry traffic for a more distant wireless/mesh secondary. So, make sure that classroom access point is close enough to the office for it to get a strong 5GHz connection for itself. That means typically one or two rooms away, depending on construction materials. If it's not close enough, you may need to move it closer. It can then provide coverage to more distant clients.
