Many people use me at school, As I am a useful tool, They use me so they can save time, However, sometimes, using me is a crime.
What am I?
You are of course
A calculator
Explanation:
The capital letters spell "MATH". Calculators are useful tools used to solve math problems, often in school. It can save you a lot of time. However, many tests forbid calculators, and using one would be considered cheating, which is a crime in some sense.
A potential answer can be:
Correction fluid.
Many people use me at school, As I am a useful tool, They use me so they can save time, However, sometimes, using me is a crime.
self explanatory. Regarding saving time thing instead of making a document again because of some petty mistake one can use correction liquid over them. Its abuse as an inhalant is a crime. Source Wikipedia