[误] School is a palace where students learn knowledge.

[正] School is a palace where students acquire/attain knowledge.

注：learn 后一般只接具体的学习内容，如 learn English(学英语)，learn to play basketball(学打篮球)等。但宽泛的“学知识”不能用 learn，而应用 acquire/obtain knowledge，因为那才是地道的表达。

参考例句：Less formally educated people can acquire professional competence 接受比较非正规教育的人可以学习专业技能