When was writing in Mesopotamia invented?

The most ancient monument of cuneiform writing in Mesopotamia was the Kish tablet, created around 3500 BC. The main writing material was soft clay. The oldest writing in Mesopotamia was pictorial. One drawing had a variety of meanings. For example, drawing an eye meant not only “eye”, but also “face”, “front”. Two vertical strokes, streams of water were interpreted as “water” and “son”. A feature of cuneiform writing was that most of the written signs were transformed into syllables of two or three sounds. Reading the cuneiform text was like solving a puzzle. Literacy in Mesopotamia was taught to the children of priests, noble persons. Schools were built at temples and palaces.