મહેતાજી ગયા એટલે નિશાળીઓને મજા.

mahētājī gayā ēṭalē niśāḷīōnē majā.

Literally: The teacher left, so the students are happy.
What it means: When the authority figure is absent, subordinates will take advantage of the freedom.
The English proverb Shah set beside it: When cats are away, mice are at play.

Also said as

ગુજરાતી કહેવતસંગ્રહ (Gujarati Kahevat Sangrah) (1923) · read from the scan by machine — the Gujarati itself is unchecked · English is machine-made and nobody has checked it yet

Heard it differently, or know we've got the sense wrong? Tell us — that is exactly the kind of correction this needs.