I want teach programming some number of students.
I want give them tasks like "write function that get some input and return some value", or "write code that read some stdin and write some lines to stdout" and they solve that tasks in some online service and execute code. This online service validate return values/output according expected values.
Ideally i want be able see some statistics for group of students, does they all solve every task, how many tries was required etc.
Does such service exist?