In Harry Potter and the Order of the Phoenix, Ron Weasley is appointed Prefect for Gryffindor, much to the amazement of everyone; it had been thought that Harry would be tipped for that job.

What year does Ron become a prefect?

Ron and Hermione were Gryffindor Prefects in their fifth year.

Why did Dumbledore make Ron a prefect?

Ron's becoming a prefect is designed to give him self-confidence which he has lacked to this point. Ron, an average wizard, feels overshadowed by the alarmingly competent Hermione and the famous Harry Potter, despite their being his best friends.