(Harlequin Superromance #1041)
A Mother to His Children (The First Family of Texas #4) by K.N. Casper
When Julie First's boyfriend proposes on the condition that she devote herself to him and his banking career, she can't flee fast enough. She's going to put all her energy into working for the school district, instead, now that she's received her master's degree in education.
The job sounds great, except for that final clause in her contract - sign a loyalty oath that promises she won't criticize the administration. Julie finds the demand odd and offensive, but she goes along until she can no longer ignore growing evidence of corruption.

School board member Rolf Murdock thinks Julie's concerns are exaggerated, but he'll help her investigate. Although his first wife left him to pursue her career, he's as charmed by career woman Julie as she is by him and his children. Soon they're investigating more than a cover-up!