Sorry, your paper isn't up to scratch. Please do it over again.The performance was not up to snuff.
not up to snuff
Not acceptable or satisfactory; not attaining a particular standard. Your papers have been very good all semester, but, frankly, this one is not up to snuff.
not up to scratch and not up to snuff
Fig. not adequate. Sorry, your paper isn't up to scratch. Please do it over again.The performance was not up to snuff.