noun
open-air classes; outdoor classroom
Refers to classes held outdoors, often in a schoolyard or park, sometimes associated with temporary arrangements or special events.
今日は天気がいいので、青空教室で授業をします。
Since the weather is nice today, we'll have class in the open air.
Compound of 青空 (あおぞら, 'blue sky') and 教室 (きょうしつ, 'classroom').