S.C.
Most of the time the preschool will ask you if they can evaluate him if they think there is a problem. Also, the circle time may just be too long for someone his age. Especially if he is not used to the daycare setting. The attention span of a child his age is about 3-4 minutes, after that you tend to lose them. But once he gets used to the routines, he should start doing better for circle time. But if you still feel anxious about it and if his teacher is worried, I would talk to his physician.