Rehearsals for this year’s Lincoln High School all-school play, “Mary Poppins,” have taken on a sense of urgency as students and directors try to make the musical as “practically perfect” as its title character ahead of its first public performance Friday night.

“Mary Poppins” is the story of a family whose dysfunction prevents them from finding a nanny who won’t suddenly quit and a self-assured nanny, “Mary,” who aims to change that.