Phillips of Birmingham was the fist team to field a team in Alabama. At that time the school was known as Central High School and they played the University of Alabama.
Football was nothing like it is today. Most likely the Central team was made up of students and former students which was the case for the next 30 years. There was not really an age limit to attend high school so some students may have been in their mid twenties and still going to school.
There was no governing body for high school sports until 1921 so the teams were often made up of whoever wanted to play for the school. The players were not always students.