This is me!
puerile (pu·er·ile): / PYOOR il | PYOO er il /
(1) childishly silly or foolish; trivial or immature
(2) relating to childhood; juvenile
[Possibly from or via French puéril, or directly from Latin puerilis meaning “boyish,” from Latin puer meaning “boy.”]
Usage: I asked for your best literary effort, yet the paper you submitted represented puerile writing at best.