Hastening to offer the prayer when the time for it begins is one of the best of deeds before Allaah, may He be glorified and exalted.
It was narrated that ‘Abd-Allaah ibn Mas’ood (may Allaah be pleased with him) said: I asked the Prophet (peace and blessings of Allaah be upon him): Which deed is dearest to Allaah? He said: “Prayer offered on time.” He said: Then what? He said: “Honouring one’s parents.” He said: Then what? He said: “Jihad for the sake of Allaah.” Narrated by al-Bukhaari (527) and Muslim (85).
Al-Nawawi (may Allaah have mercy on him) said:
This hadeeth encourages us to offer prayers regularly on time. It may be understood from it that it is mustahabb to offer them at the beginning of their time, because it is more on the safe side, and we should hasten to do them on time. End quote.
Sharh Muslim, 2/265
It was narrated that Umm Farwah (may Allaah be pleased with her) said: The Messenger of Allaah (peace and blessings of Allaah be upon him) was asked: Which deed is best? He said: “Prayer offered at the beginning of its time.” Narrated by Abu Dawood (426); classed as saheeh by al-Albaani.
Imam Ahmad (may Allaah have mercy on him) said:
The beginning of its time is dearer to me except in the case of two prayers: ‘Isha’ and Zuhr, where one should wait until it has gotten cooler if it is hot.” End quote.
It is also mustahabb to hasten to break the fast. A number of ahaadeeth have been narrated concerning that, such as that which was narrated by al-Bukhaari (1957) and Muslim (1098) from Sahl ibn Sa’d (may Allaah be pleased with him), that the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “The people will still be fine so long as they hasten to break the fast.”
Thus it is clear to you that it is mustahabb in your case to hasten to break the fast and pray Maghrib at school.
But that is only what is recommended. If it is too difficult for you, and you fear that you will miss your ride or you will be late getting home, there is no sin on you if you delay the prayer and do it when you get home, so long as you think it most likely that you will get home before the adhaan of ‘Isha’. You could break your fast with a few dates that you carry with you on your way home.
But if your question is about not fasting in Ramadaan because of hardship caused by work, we have discussed that in the answer to question no. 43772
May Allaah help you to do that which He loves and which pleases Him. May Allaah reward you for your keenness to obey Him.
And Allaah knows best.