I couldn't find any translation in my dictionaries. Though. In context it seems to mean 'always'?! 这孩子老在班上捣蛋。 Is this correct.
Cheers
老在 is not a word. It's an adverb followed by a preposition.
老 means always or constantly.
在 is just a preposition, here it would be 'on' to go with 班上(the class)
So it's: This kid always create troubles on the class.
老 is an adjective, means old.
It then be used as an adverb, long time, always, since old means long time.
For example, 这孩子老捣蛋。商店里老有人偷钱包。
在班上 is a adverb phrase means location, where to happen.