.....the problem of WINDOWSSSS........

in the class i can't see .... well i can't see the board.... why??????? because the reflection of the sunlight produces a shine,,,,,, and i can't see what teachers....... writte...,......... we already talk with the principal.... and put somo paper in the windows.... but the guys that study at night... removed them...... any solution?????? pleasssse help...... me........