The student pilot reported that he completed the preflight and pre-takeoff checklist and the airplane was operating normally. He set the power at 6,200 rpm's for takeoff from the private grass airstrip. When the airplane had reached about 200 feet above ground level, the engine rpm's dropped to 4,000 rpm's. He executed a forced landing to a neighbor's yard. During the landing roll, both wingtips hit trees and the airplane slid sideways and the left wingtip hit a house window. The airplane wreckage was taken to a hangar for inspection. The engine was started and it idled normally. The throttle was advanced to 5,000 rpm and it ran smoothly. No deficiencies were found that would have precluded normal engine operation. Aircraft records indicated that the last annual maintenance inspection was conducted on April 3, 2007. The student pilot, who had a total of 266 flight hours, did not have an endorsement for the make and model aircraft in the last 90 days. His Student Pilot Certificate, which is valid for two years, had expired on February 29, 2008.