The win gave Ingomar coach Norris Ashley his ninth state championship in 39 years at the north Mississippi school.
Ashley has won five boys titles and four girls crowns.
The Falcons (30-6) never trailed after the first couple of minutes. They led 29-23 at half and 45-38 after the third quarter.
When McAdams (23-8) cut the lead to four midway through the fourth quarter, Carnell scored four straight points to extend the lead.
Patrick Lewis scored 21 to lead McAdams.
The Falcons denied McAdams a championship sweep. The McAdams girls beat Myrtle for the 1A girls title.
Read more in Friday's NEMS Daily Journal newspaper.