。、。
I'm the one who found her. She was unconscious, so I carried her to the nurse's office.
Literal
Found [nominalizer-の] [topic-は] I is. Consciousness [obj-を] was-losing [because-so-ので], nurse's-office [to-に] carried.
A cleft sentence identifying the finder: 見つけたのは僕です ('the one who found is me'). 喪う ('to lose') is a literary/formal variant of 失う ('to lose') used specifically for things you 'ought not lose' like consciousness or dignity — here writing 意識を喪う ('lose consciousness') in a slightly elevated register. 保健室 ('nurse's office / health room') is the standard Japanese school infirmary where sick students rest. ので is the causal subordinator 'because, so' — slightly softer than から.