The abstract proofs of geometry all refer to concrete geometric reality, such as the proof that shows that "the opposite sides of a parallelogram are equal." If the teachers put out a little extra effort, then by rights students in seventh and eighth grade should all have experience making measurements with specific examples. This will make it much easier for them to understand the abstract concepts.
抽象的幾何證明其實也是從實驗幾何而來，例如證明「平行四邊形的兩個對邊相等」，如果老師多費點功天，國三之前都應有具體測量的經驗，從具體操作到抽象概念，照理說會事半功倍才對。