Catherine Peay, a 37-year-old public school teacher, is accused of having sex with a 12-year-old pupil.  A bond hearing was postponed Monday to give the woman time to get a lawyer.  She told Judge Mary Beth McCormick of Montgomery County District court that she had learned only 20 minutes before the hearing that lawyers with the Maryland State Teachers Association would not represent her.  Peay was arrested hours after a Montgomery County Park Police officer discovered her and the 12 year old boy in a park at about 3:15 a.m. Friday, running and hiding from his cruiser, according to court documents.  The boy allegedly told the officer they had been kissing and that they have been having a sexual relationship since July.  Once Peay was confronted with the pupil's statements, she admitted having sex about four times with the boy, who was in her summer school class.  Peay could be sent to prison for up to 65 years if convicted of second degree rape, child abuse and other charges.  She is being held in lieu of $500,000 bond.