As far as I know, MUST and HAVE TO are often interchangeable.
When talking about school rules is it better to use MUST or HAVE TO?
For example (teacher speaking):
Students must do their homework. / Students have to do their homework.
Students must be on time. / Students have to be on time.
Students must turn off their mobiles. / Students have to turn off their mobile.
And what about speaking in the first person?
I must wear a uniform / I have to wear a uniform. Etc.
Thanks a lot.