All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
If your wife's work in this school involves being in seclusion with non-Mahram men or exposes her to temptation, her work is not permissible and it is your duty to prevent her from it. But if she observes the Islamic etiquettes in her work by avoiding being in seclusion with non-Mahram men, adhering to the proper Hijab, avoiding soft speech when talking to men, and talking to them only when necessary, or that she had laid a condition upon concluding the marriage contract that she would work, then you have no right to prevent her from work.
In case she had not stipulated (at the time of marriage) that she would work, you can prevent her from going to work. For further information, refer to Fataawa 82399 and 88048.