If my daughter is sleeping from the time she comes home from school (3:30) and sleeps right through until the next morning (7:15) should i be concernd?

Look into the cause: She should be screening for an under-active thyroid, anemia or other medical conditions with blood testing. If all are normal, then sleep apnea should be considered. She may be getting a sufficient quantity of sleep, but lacking the quality. An overnight study is done to evaluate her sleep stages, leg movements, breathing, heart rate and oxygenation at night.

Seems excessive: 17 hrs of sleep is considered excessive for anybody except newborns and infants. A school age child can sleep 10 - 12 hrs easily. I would first talk to her, check for other issues, make sure she is not waking up at night. Then talk to her pediatrician for a thorough check. Is she taking any medications?

Not normal: It's not normal to sleep this much for any age. There might be something causing this and it's a good idea to see a doctor to get this evaluated.