First day of September.

That means almost all students will start new educational year tomorrow. -> That means almost all students will start the new school year tomorrow.

I am intrestested, is first day of September first day of studing in all countries? -> I am curious, is the first day of September the first day of school in all countries? ("Curious" is better than 'interested', though grammatically 'interested' is okay. But most native speakers would say 'curious'.)

Is there different in dates? -> Are there different dates (to start)?

*In the US, the new school year starts at the end of August or the beginning of September (it depends on which state you are talking about.) But I know in Japan, the school year starts in April. So, yes, I think many countries are the same, but there are some that are different. :)