Jews, for example, hold that the first Commandment is Exodus 20:2, “I am the LORD thy God, which have brought thee out of the land of Egypt, out of the house of bondage.” No Christian group, however, believes this verse to be a commandment.
Catholics and Lutherans take Exodus 20:3-6 as the first Commandment (having no god before God and making no graven images). Jews take this to be the second Commandment. Protestants and Orthodox Christians divide these into two Commandments, Exodus 20:3 (the primacy of God) and 20:4-6 (graven images).
By contrast, Protestants and Orthodox Christians count Exodus 20:7 (“Thou shalt not covet thy neighbour's house, thou shalt not covet thy neighbour's wife, nor his manservant, nor his maidservant, nor his ox, nor his ass, nor any thing that is thy neighbour's.”) as a single commandment, while Catholics and Lutherans divide it into two, with the neighbor’s wife (“lust”) being separate from the other property (“greed”).
The problem arises, of course, because Exodus 20:2-17 contains 16 verses that must be divided into just Ten Commandments, as per Exodus 24:38 and Deuteronomy 4:13, but without any clear demarcation of which verses (a medieval numbering convention) belong to which commandment.
So, given that each religious group has created its own list of Commandments, any government plaque or memorial or display must by necessity take a sectarian position by choosing which of the three competing numbering systems to use, therefore establishing one set of Commandments above the others as the government’s official choice. Who among religious believers wants to explain to his or her child why the classroom or the courthouse displays religious texts telling that child that his or her religion is the wrong one?