You were sleeping during our English class today, weren't you?
You were in dreamland during our English class today, weren't you?
この場合、次のように言うことができますよ。
ーYou were sleeping during our English class today, weren't you?
「今日英語の授業中寝てたでしょ？」
during our English class で「英語の授業中」
ーYou were in dreamland during our English class today, weren't you?
「今日英語の授業中寝てたでしょ？」
to be in dreamland で「夢の世界にいる」＝「寝ている」ことが言えます。
ご参考まで！
カナダ 
