Is it possible to run multiply scripts from shell?

if shell sript a.sh starts, shell script b.sh has to start at the exact time.
they have to run side by side.

example:
in shell script i wan't to run a ping test to www.google.com with the output written to a textfile.
in shell script i wan't to run a ping test to the dns server of google (8.8.8.8) with the output written to a textfile.

a.sh
#!/bin/bash
$(date +%Y%m%d%H%M) >> /mnt/pinga.txt
ping -c 10 www.google.com >> /mnt/pinga.txt

b.sh

#!/bin/bash
$(date +%Y%m%d%H%M) >> /mnt/pingb.txt
ping -c 10 8.8.8.8 >> /mnt/pingb.txt

both scripts are a simple example.
So, in my mean script (dualscript.sh) i do this:

#!/bin/bash
#######
script1=`/mnt/a.sh`
script2=`/mnt/b.sh`
#######
sh $script2 & sh $script1
done

dualscript.sh now first run a.sh when the script is done, then he starts b.sh.
but i don't want that. they have to start at the same time.
i found some related topics for running parallel scripts, but not for OPENWRT.
somebody can help me ?

Just start both scripts in the background and then wait till both pid's are finished
so it will be:

#!/bin/sh
#######
script1=`/mnt/a.sh`
script2=`/mnt/b.sh`
#######
"$script2"&
"$script1"&
wait

This way all child processes have to finish before the main script continues.
Also openwrt doesn't have bash, so if the scripts didn't run before that is the reason.

I think that is not the issue. I've just tried what he/she posted, and it works. As he/she said this were just examples, I'm guessing it's a mistake in the real scripts.