Running multiple containers on one EC2 instance but each container having different ENV variables

Question

I have a school management system written in Laravel. All schools use the same codebase, which means they all use the same GIT repo and git branch, with the only difference being the database and subdomain.

Each school has its own database and subdomain, for example, school1.schoolsystem.example.

My problem is determining the best approach to take in the AWS platform.

Create a separate EC2 instance for each school.

Containerize each school (using the specific ENV variables) and add to an EC2 or ECS instance (Can multiple containers run in the same instance?)

Which method is the most cost-effective and convenient for CI/CD?