While lunches and breaks are highly recommended, I do not know of an employer that is mandated, by law, to give them. This includes, no lunch break. While I am sure there are laws concerning different types of employment, the norm is, no mandatory breaks must be given.
In most cases, there should be breaks of at least 10 minutes for each four hours worked. If you work over five hours in a day you should get meal breaks of at least 30 minutes and this applies for over ten hours worked as well. The time period can vary from employer to employer as they all use different methods to allocate and calculate the break periods.
Labor laws entitled you to a 15 minute break during a 6 hour shift and a 15 break and 30 minute lunch during an 8+ hour shift. There are no laws entitling you to beaks during a short 4 hour shift. Some companies offer it but it is not required. Check with your HR department about it.
No one has to get a break in a four hour shift unless you work a job which requires you to be in a fresh air suit or pumped oxygen in which you work fifteen then off fifteen for health reasons but I think your just a kid with a part time job you don't need anything but potty breaks unless you have health issues than your employer is required to give you reasonable accommodations but the health condition must be well documented and you must still be able to do the job efficiently with the accommodations