You can meet building standards/codes very easily by installing a down
draft vent under the kilns. It would only take the cost of the vent and a
hose to vent it out a window. The custodian did the installations so there
was no additional cost for that. I had two unvented kilns in the high
school building (building from about 1919). We put vents under both the old
kiln and the new one. They vent out a window opening that has a panel cut
to fit the two vent pipes.
See if there is a room where the kilns could be placed close to a window
(idealy as close to the art room as possible)