PROG GLM syntax -- contrasting groups using LSMEANS

proc glimmix data=kaz2.Year2AnalysisSample;
class SCHOOL_NAME grade_level race_cate;
model
&z_post = treat
grade_level
/solution ddfm=kr dist=normal link=identity s ;
random SCHOOL_NAME;
covtest /wald;
lsmeans grade_level / diff;
run;