YOU don't get any tax breaks for being a full time student, your parents do.
Anything over $6300 will be taxed. At $12,000 income, your tax is $570 (10% of 12,000-6300). If you had $4500 withheld, you'll get back $3930 (unless that $4500 includes FICA. You don't get any FICA [social security & medicare] back).
By the way, $4500 withholding on $12,000 of income, is excessive, as was $2300 on $6500 the year before. In fact, so excessive, that the only likely way that happened was for you to have asked for "additional" withholding.
