At St. Mark's, 2017-18 was among the most successful years overall athletically in the history of the School. All SM teams—varsity, JV, and 3rds—amassed a record total of 357 victories for an overall winning percentage of .600. To accomplish this, 28 out of the 47 St. Mark's teams (60 percent) posted records of .500 or better. Varsity teams won 59 percent of their scheduled games, for a total of 207 victories.
The only rival year, at least percentage-wise, was probably 1975-76. That fall, all varsity teams were unbeaten (there were only two fall varsity teams at all-male St. Mark's back then: both varsity football—7-0-0—and varsity soccer—9-0-3—were undefeated). In 1975-76, all SM varsity teams (there were only nine of them) won 70 percent of their games (74-31-5) with only one varsity team posting a sub .500 record (and that only by a single game). Overall, including club teams, JVs, 3rds, and more, St. Mark's won 69 percent of all scheduled games, and when you add in the successes of the Southborough School (their only full-season team, field hockey, had only one loss in 10 contests), the overall mark was 115-55-11, a .666 winning percentage.
Still, for a fully co-ed, modern St. Mark's athletic schedule, this past year's .600 winning percentage and 357 overall wins appear to be new records. And for the record: in 2017-18, SM girls won 63 percent of their games while SM boys won 57 percent.