Gradebook

Right now, I have the lower level cutoffs for letter grades set according to what is available in the pulldown menu, however, we want to set the default lower level cutoff to a decimal point other than the default. we would like to set the cutoffs to (for example) 84.5, 89.5, 94.5 rather than 84.9, 89.9 and 94.9.

I haven't been able to locate anything on this.... I might be looking in the wrong place

Thanks in advance