Many people choose to use Mint Mobile. They offer a number of subscriptions with different amounts of mobile data so you can customise it to your needs. Mint Mobile also offer eSims for compatible phones so you can activate the SIM remotely without waiting for a physical SIM to be sent in the mail to your college dorm.  Click HERE to read more about Mint Mobile and their subscriptions.

You could also choose to wait until you arrive and purchase a SIM in person at a place such as the mall, Walmart, Target etc. You would likely be better buying a pre-paid SIM where you pay in advance each month, then you can control which months you pay for. American mobile companies also have physical stores so you can stop into one of those if you have further questions, but these tend to be far more expensive than those found online/in supermarkets mentioned previously. 

Students also ask about using roaming abroad as some UK plans offer the use of data abroad as part of their plans. This usually doesn't extend to the amount of time you will be in the US in one go and will likely be subject to very hefty fees once you go over.