I seem to have low self esteem when approaching new people or speaking up in class. How can i overcome being shy?
The best way to overcome this sort of shyness is through practise; realising that you are entitled to speak and be shown respect for your opinions and not worrying about what others think.
None of those things are necessarily easy. Many people suffer with this. Take it in easy steps. To approach new people, consider those you feel most comfortable approaching first. Think about what you will say before starting conversation. Ask them something about themselves and listen to what they have to say. It may feel awkward at first but will get better with time.
When trying to speak up in class consider why you need to. You are in class to learn, so sometimes you need to speak. Everyone is entitled to ask questions and your teachers will be pleased that you are showing interest. There is nothing more upsetting for a teacher than a silent and disinterested group of students! Don't worry about making mistakes or giving the wrong answer either. Anyone who mocks or laughs at you is plain ignorant and rude. It is only from making mistakes that we all learn.
I hope that has given you some pointers.