The high school football playoffs hit the semifinals tonight in what's shaping up as a season of change at the top.

Gone are defending champions Grayson, Valdosta, Cartersville, Benedictine and Macon County. Also out are Lowndes and Manchester, teams that entered the playoffs ranked No. 1.

"The ones that were the front-runners aren't there now," said North Gwinnett coach Bill Stewart, whose team has won 12 straight after losing its opener. "You've got four teams [in Class AAAAAAA] that have kept grinding and emerged, and that's a cool thing. Everybody has the mindset that we can all play with each other."

Thirteen of the 32 survivors have never won state titles. Among those, No. 5 North Gwinnett in AAAAAAA and No. 2 Hapeville Charter in AA are the highest-ranked teams left in their brackets. Blessed Trinity and Greater Atlanta Christian also have excellent shots at breaking through for the first time.

Here are more things to know about the penultimate weekend of the season.

*Newcomers: Four schools are in the semifinals for the first time. Those schools, with their first seasons of varsity football in parentheses, are Rabun County (1949), Mount Zion (1956), Lee County (1971) and Heard County (1972). Carver-Atlanta is in the semifinals for the first time since 1968.

*Regulars: Twelve of the 32 semifinal teams made the final four last season. Buford has made it 11 consecutive times, winning each of the previous 10. Eagle's Landing Christian has made it seven in a row. Colquitt County is in for the eighth time in nine seasons. Calhoun is in for the eighth time in 10 seasons.

*Dramatic arrivals: Mount Zion, a Carroll County school of some 400 students, defeated Manchester, the No. 1-ranked Class A public-school team, 10-6 in the quarterfinals after C.J. Ackles threw a 9-yard touchdown pass to Iaan Cousin with 23.9 seconds left. It came at the end of an 88-yard drive that started with 1:55 left. That was the only semifinal won in the final minute, although Buford had a close call after trailing third-ranked Stockbridge in the first quarter of a Class AAAAA game. Hayden Olsen's 24-yard field goal with 6:08 left broke a 17-17 tie.

*Turnarounds: St. Pius is in the semifinals despite a 2-9 finish in 2016 and an 0-5 start to 2017. St. Pius' lone state title came in 1968. Warner Robins is another nearly worst-to-first scenario. The Demons were 3-7 last season.

*Best matchups: No. 1 Rome, the defending champion, plays host to 11-time champion and second-ranked Buford. St. Pius travels to archrival Marist in AAAA. They've met 52 times, with Marist winning 37, but this is their first meeting in the playoffs. The most competitive games, according to the computer Maxwell Ratings, are Coffee at Tucker (Tucker favored by one) and Colquitt County at Brookwood (Brookwood favored by three).

*2016 rematches: Seven of the 16 games are rematches of 2016 playoff games, most notably Rome's 16-7 victory over Buford in the AAAAA final. The AAA semifinals have a pair of rematches as Greater Atlanta Christian beat Peach County 13-7 last year and Cedar Grove beat Calhoun 47-21. Both winners are favored again. The other 2016 rematches favor the losing teams this time. Last year, Colquitt County beat Brookwood 66-35, Mary Persons beat Blessed Trinity 28-27, Mount Paran Christian beat Athens Academy 17-10, and Emanuel County Institute beat Irwin County 44-25.

*Heavily favored: Eagle's Landing Christian has won 34 consecutive games and is given an 81 percent chance of defending its Class A private-school title by the Maxwell Ratings.

*Underdogs: Three unranked teams are in the semifinals - McEachern, Carver-Atlanta and St. Pius. McEachern and Carver had been ranked earlier in the season. St. Pius started the season 0-5.

*Coin flips: Seven teams are playing at home after winning coin tosses. That's per GHSA rules when region champions (or other same-seeded teams) meet in the semifinals. Since 2008, when the semis were taken out of the Georgia Dome, teams winning coin tosses are 33-21 in the semifinals. The seven that won the coin toss for this week are Lee County, Rome, Warner Robins, Marist, Greater Atlanta Christian, Cedar Grove and Heard County.

*Long road trip: The 278.5-mile distance between Class AA semifinal opponents Brooks County and home-standing Rabun County will be the 16th-longest in state-playoff history, according to researchers at the Georgia High School Football Historians Association. That's out of 4,811 state-playoff games since 1948. It's the longest distance this season out of 19 playoff games exceeding 200 miles.

*Short road trip: The 3.5-mile distance between AAAA semifinal opponents Marist and St. Pius is the 11th-shortest in playoff history, but only the third-shortest this season. A first-round game in Macon between First Presbyterian and Tattnall Square set the all-time record at 2.1 miles.

*Next: The 16 winners will advance to the finals Dec. 8-9 in Mercedes-Benz Stadium. That ends a nine-year run of the championship games in the Georgia Dome, which was imploded last week.

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