предлог

[Cory_ander]

С тех пор попасть внутрь учебного заведения можно только по отпечатку пальца.

Since that time one can get into the school only BY (??) fingerprints

[anna-yel]

Since that time the school introduced a fingerprint access control system. Может так?

[victoriska]

Можно схитрить: only after providing his / her fingerprints

[Тимурыч]

Since that time you can get inside the school building only after having your fingerprints scanned

[ilonanew]

Ever since one can get inside the school only through providing fingerprints