No. of photoelectrons vs frequency and intensity
The number of photoelectrons per incident photon doesn't really vary with photon energy (frequency). Particularly a photon won't eject multiple "photoelectrons." By definition a photoelectron is a loosely bound electron (i.e. not in an atomic or molecular orbital) which is ejected in a one-to-one basis by a photon and thus satisfying the equation $$ \rm{KE}_{electron} = \rm{h}\nu - \phi$$ where:


$ \rm{KE}_{electron}$ is the kinetic energy of the electron
$\rm{h}\nu$ is the energy of the incident photon
$\phi$ is the work function for the substrate (how much energy it takes to remove electron from substrate). 


In general the substrate would be a metal and the electron would be in the metallic (electrically conducting) layer. 


If the electron is bound in an atomic or molecular orbital then the
technique is Electron Spectroscopy for Chemical Analysis (ESCA).
If the photon is too energetic then it penetrates too deeply to eject an photoelectron.


The gist of the above conditions is that photoelectrons are created with relatively low energy photon just above the needed threshold given by the work function, $\phi$. 

Another aspect of this is that a photon can only interact with one electron at a time. However if the photon is greater than $2\phi$ in energy it is possible that the electron can receive enough energy to knock yet another electron out of the metal. These two electrons wouldn't be "photoelectrons" since they don't fit the equation. They would be noise in the experiment and the experiment would need to be designed to minimize counting such electrons. So the ejection of multiple electrons by a photon is possible, but not multiple photoelectrons by definition.