To play truant (be absent from school without permission).
play the wag
play hooky
To play truant; to avoid (informally: skip) school, work, or other dut…
go on the mitch
to skip school; to play truant
French leave
A departure taken quietly and unnoticed, without asking for permission…
take French leave
To leave quietly and unnoticed, without asking for permission or infor…
take liberties
To act on one's own authority, without asking for permission.