Both you and your kids can expect to go through an adjustment period that may last a few months.  The road may be bumpy for a little while, so be prepared to hang in there.  Your kids may feel a little overwhelmed at the beginning, but explain to them that this is normal and they need to give themselves some time.  Encourage them to get involved in as many activities as they can at their new school.  This will help them make new friends and find something that they are passionate about that they can stay involved in throughout the year.  Encourage them to be themself and not try to act like something they aren't just so they can fit in or feel cool.  
 
Depending upon the school, they may find that the school work is more or less challenging.  Remind them that there are lots of people at school that want them to succeed, so they need to ask for help if they feel like they are falling behind academically.  Their teachers and school counselor are all there to help them adjust.  It may help them to keep a journal during their first few months of school to write about things that are difficult or frustrating.  Not only will that help them to express their feelings, it may also be interesting for them to reflect on later in their life.  
 
Unfortunately bullying seems to happen everywhere.  That doesn't mean your child will automatically be bullied, but let them know that it does exist so they're prepared. If they find themselves in an uncomfortable situation encourage them to ignore the bully and talk to an adult about what's going on.  It's great to hear that school uniforms are being used.  Uniforms help to protect the kids from some forms of discrimination in regards to what brand of clothing they wear, or how expensive their clothes are.  
 
As long as you keep the lines of communication open, you and your children will be off to a good start.  Let them know that as issues or problems arise they can always come talk to you about it.  
 
Boys Town National Hotline
1-800-448-3000