Cleaning Concrete Countertop Material?

Hi everyone and thanks in advance for tips. I am cleaning the desks in my church school. Some are painted wood and they are coming clean OK, but there are some that are like a poured concrete. That is what they look like anyway. They also look a bit like countertop material.

Anyway I was trying to clean them today. They started to come clean when I sprayed bleach water on them but you could see it was sprayed. Then i got a sponge with the green scrubby thing on the other side. For 15 minutes I scrubbed that desk top. Oh yes, it came clean but it still is dirty plus I have 12 desks in that room to clean. I have not tried vinegar yet. That is the only thing I can think of that my nose could tolerate. Someone has suggested a Gorrllla or gooey something but she said it smells, oooohhhh really smelly. Don't want that. Any suggestions, please help!

Sandy from Baltimore