I believe the answer is: The posting would not be in violation of the clause because there is a learning purpose to the items
Establishment clause banned the government officials to create a legislation that force citizens to respect a certain type of religious establishment. Ten commandments was made as basic rule of life for Christians.
Only posting the teachings could not be considered as the government 'forcing'the citizens to obey it, unless they made a legal punishment for the people who disobey them.
