Is it possible to enter a .5 mark (i.e. 19.5) for a standard? One of my teachers tried this and received the following error message: "Validation errors must be corrected on the selected score before saving".
You can include multiple decimal values while creating the Numeric grade scale which would help you fix this error message. You should be able to select a character to include in the grade scale values from the Include menu where a Decimals menu appears if you are using this grade scale for standards.
You can find more information about the Numeric Grade Scale in this document on GradeScales.
Please let us know if this helps.