.... And the principal — Marcella Sills, who joined PS 106 nine years ago — is a frequent no-show, sources say.

Sills did not come to school last Monday. On Tuesday, she showed up at 3:30 p.m.

On Wednesday, The Post found her at home in Westbury, LI, all day before emerging at 2:50 p.m. — school dismissal time. Wearing a fur coat, she took her BMW for a spin.

She showed up at school Thursday, but not Friday....