When you say "not working" exactly what is happening?
It may be you need to do a for loop rather than piping into xargs:
for job in $(bjobs | cut -d' ' -f1 | sed '1d')
do bmod -q high $job
I'm not familiar with bmod so am not sure if your command syntax is correct. What happens if you pick a single job and run the bmod -q high on it?