Aron Nel Steinke’s “Mr. Wolf’s Class” books, of which “Lucky Stars” is the third volume, have been wholesomely winsome and charming. The latest installment in the series shows the care and growth the character and their relationships, which have blossomed since their first day of school (which is the subject of the first book). As ever, Mr. Wolf and his class of rambunctious (but sweet) fourth graders learn life lessons, develop deep friendships, and overcome the challenges of growing up.