It's not even just interfering with teaching.roostuf said:yes, its a public area, you have the right to pray there as long as it does not interfere with the school teaching.
If you are a public employee and are acting in official capacity, you cannot take an action that would be seen as endorsing a religion. It is a violation of the First Amendment. Engel v. Vitale ruled it illegal for a school to compose an official prayer and mandate its students to recite even though you can refuse to do so.