noun
training school; training institute; practice hall
A facility or institution where one practices or trains, often for arts, sports, or vocational skills.
彼は毎日、柔道の練習所に通っている。
He goes to the judo training hall every day.
この練習所では、ピアノの個人レッスンが受けられ
You can take private piano lessons at this training institute.
教室 is a classroom or lesson space, often in a school setting; 練習所 emphasizes practice and training rather than formal instruction.
Compound of 練習 (practice) + 所 (place). The exact historical derivation is uncertain, but the meaning is transparent from its components.