How can I pass the name of the variable inside a for statment
I have a script something like below:

classA=12
classB=14
classC=16
# classD = 20

all_class="classA classB classC"

for i in $all_class
do
echo $i = $($i) #<---- this one not work
#echo $i = $(echo $i) # <---- this one not work too
#echo classA = $classA # <----- it can pass the classA = 12
done

Also, how can i do if i don't know how many class will be there and i don't want to change the all_class value ?