Waitress attitude over tip

We were a large group of under 18's and had a limited amount of money since our money is provided by our parents not by ourselves. The waitress lost her temper when we did not give the full 10% tip,but we gave as much money for a tip as we possibly can, about 7.5% tip at least. She pointed at us and gossiped at the other waiters and embaressed us. Very unsatisfied with the service that was provided to us. Will most likely not come again. Utterly dissatisfied.