Firstly, you wouldn't need blu tack because gum is just as sticky. You don't have to waste your money on buying blu tack.
Secondly, you won't talk because you will be to busy chewing. This means you won't get in trouble for talking.
Thirdly it tastes good and you won't need any other food. This means you can eat your gum for the whole day and save money on buying lunch.
Lastly if you have bad breath or forget to brush your teeth it will do the trick. This means people won't tease you for having unbearable breath.
Therefore, we should totally be allowed to chew gum at school.