childishly       
adverb  usually disapproving uk/ˈtʃaɪl.dɪʃ.li/ us/ˈtʃaɪl.dɪʃ.li/
 (成人)孩子气地,幼稚地
in a way that would be expected of or appropriate for a child
  We felt he was behaving childishly and irresponsibly.  我们觉得他的行为很幼稚,不负责任。 
 The tests were childishly easy.  测试简单到幼稚。 
 See: childish
 - More examples
 - The noise came from a bunch of grown-ups acting childishly.
 - The meal is childishly simple to make.
 - The writing becomes childishly breathless at points.
 - They entertained themselves by childishly bullying their workmates.