Use "schoolboyish" in a sentence

1. such schoolboyish bluntness

2. " I don't understand this schoolboyish conversation, Lambert, and I'm ashamed of it

3. Her best qualities were, as a rule, buried under the most harum-scarum wilfulness, the most schoolboyish pranks, almost verging on buffoonery; they were rarely noticed, and, when they were, were hardly believed in, so that now her extraordinary brilliancy was accompanied by an eager whisper of amazement among all