no, you can not change schools under your M1 visa.
your M1 visa is valid for 1 year (or 2) after entering the USA.
you can leave the USA for 2-3 weeks vacation, and reenter. Be sure to go to the immigration office at the airport before leaving the USA.
if you change school, you have to do a new request to the US embassy or the immigration office in your US state.
if you want be out of trouble,I suggest you to see the US immigration. There are so many different VISA in the USA and each case is different, noone on this forum can real advice you what to do. Check with the US immigration in your area.(or US embassy)
BTW, if you did already an initial M1 application, the 2 nd application should costs you less and iprocess should be more faster.I said It should be...