This is the area around Gropp Lake in Yardville, on the border of Hamilton Township. The school pictured is on the east side of the lake.
The above area is across Rt 524/South Broad Street. The lake continues under the roadway and empties out into Crosswicks Creek, which one can see through the trees in these photos below (second and third from the bottom), I followed it back in the neighbourhood across the road. Crosswicks creek continues south and meets up with the Delaware in Bordentown, see the above link.