shell - Unable to run multiple scripts in parallel -

i unable execute 2 scripts in parallel through shell script.

i have 3 scripts: script1.sh, script2.sh , installpackages.sh.

my requirement script1.sh , script2.sh have run in parallel in background , after completion of script1.sh , script2.sh, installpackages.sh should executed.

selid1t601.xayybol.74> vi script.sh exec script1.sh & exec script2.sh &  installpackages.sh 

can please suggest how can execute script1.sh , script2.sh in parallel?

since executing scripts in background running in parallel. thing need wait ensure scripts have been executed before proceeding final step. need say:

exec script1.sh & exec script2.sh & wait installpackages.sh 

from manual:

wait

   wait [jobspec or pid ...] 

wait until child process specified each process id pid or job specification jobspec exits , return exit status of last command waited for. if job spec given, processes in job waited for. if no arguments given, active child processes waited for, , return status zero. if neither jobspec nor pid specifies active child process of shell, return status 127.