Always wear a smile on your face whenever you are around them. Do not make them feel that their presence has put you on a high alert. Instead, keep a happy face. Make sure that your smile does not have an element of sarcasm to it. Be sure to do away with the smile if something bad happen to them, for example if they get scolded by the teacher, trip over something, get a bad grade on a text, etc.
Make it a habit to say or wave “Hello” to them whenever you pass by them or have them at a hearing distance. Just because they are rude does not mean you start ignoring them or showing attitude.
Be nice and helpful to them whenever you get a chance. Find out how you may be able to help them through a problem and then start acting on it without wasting too much time. If they need a pen, offer yours if you have an extra one. If they are lifting something really heavy, give them a hand. If they need help with a mathematics equation, guide them through it. Be careful while offering your help though, as their problem might be something personal and therefore they would not like you meddling in it.
If you find them giving dirty looks to you, smile and wave at them so as to say “Hey.” They will surely be tempted to wave back, or at least your actions will make them know that you have taken notice of them and may discourage them from giving dirty looks to you, for a while at least.
Try to strike a conversation with them. Keep it short and pleasant. Try to compliment the dress that they are wearing, you’re their hairstyle.
If they try to make bad things happen to you, keep your cool, say thanks politely and then casually walk away. Try to make your thanks sound as genuine as possible instead of sarcastic. No matter what happens, do not retaliate either verbally or physically.