let out of (something or some place)
To conclude, dismiss from, or be dismissed from some scheduled activity, such as school. We let out of school at 3 o'clock each day, so I can get over to you by around 3:30. We were let out of camp early today.
let (someone or an animal) out of something
and let (someone or an animal) outto permit someone or an animal to exit from something or some place. Would you please let Ed out of his room? Please let out Ed.