Older Taiwan and Hong Kong usage. Mainland China standardized on 幼儿园 since the 1950s, but 幼稚园 still appears in Taiwan media and older Mainland writing. It was borrowed into Chinese from Meiji-era Japanese (幼稚園) in the late 1800s.
mistakes
On the Mainland, prefer 幼儿园 in modern speech and writing. 幼稚 by itself now mostly carries the negative meaning "childish, immature," so younger speakers may find 幼稚园 sounds old-fashioned or Taiwanese.