What is the ruling on continuing a romantic relationship with a girl during study – without seclusion or meeting outside school – and does sin result from that, and what do you advise me to do?

You must avoid this girl and cut off all communication with her, because it leads to temptation. If you are sincere with Allah in this, good will befall you. You are not responsible for this girl, for Allah will not abandon her if she is religious and of good character. If you find a way to marry her, which is what the Prophet, peace and blessings be upon him, encouraged when he said, "Nothing like marriage is seen for two who love one another," then it is a good matter. Otherwise, cut off all ties with her.