Shelby County Jail, Associated Press
This photo provided by the Shelby County Jail shows longtime Alabama schoolteacher Daniel Montague Acker Jr., 49, who was jailed Wednesday, Jan. 4, 2012, on sexual abuse charges. Acker taught for years in the Shelby County school system, where officials said he is no longer employed.

ALABASTER, Ala. — A longtime Alabama schoolteacher is jailed on charges of sexually abusing one of his fourth-grade students, and police say he has told them he molested more than 20 other girls over his 25-year career.

Police in the Birmingham suburb of Alabaster say 49-year-old Daniel Montague Acker Jr. is charged with three counts of sexual abuse, and additional charges are possible.

Authorities say a girl came forward last week claiming Acker molested her three years ago, when he was a teacher at Thompson Intermediate School. Acker retired that year but continued working as a substitute bus driver in Shelby County.

Alabaster police say Acker confessed to molesting that student and told them about the other girls.

Acker's lawyer didn't immediately return a message seeking comment.