What is the best way to enjoin good and forbid evil upon Muslims who are negligent in their religious duties such as prayer, hijab, and dealing with foreigners in a foreign school, and am I sinful if they do not respond to my call and antagonize me because of my full hijab?

You must denounce evil with knowledge, gentleness, kindness, and a good approach. If you do so, you have fulfilled your duty, and their rejection will not harm you. You should continue to advise them as long as you do not predominantly believe that they will not benefit, or if you fear a greater harm. In such a case, you must be careful not to associate with them. A good example can have a more profound effect on the one being called to the truth. We also advise you to be patient with the harm that results from adhering to religion and to pay no mind to the words of those who spread doubt.