Is going into an A school in the service similar as enrolling into a 4 year college or just training prior to the job?

A School/military training teaches you about how to do the work for a "specific" job. It normally lasts only a few weeks/months. 

Military schooling is for training for a job - NOT college.

It is training for your military job.  It is not similar to college.  A training is short for Advanced Individual Training.  All new service members first go to basic training, which is the well known boot camp.  After boot camp, the new serviceman then goes to A school, in which he learns how to do his MOS (Military Occupational Specialty).  Using my BIL as an example, upon joining the Navy he went to boot camp.  After that, he went to A training to learn his MOS as a Corpsman.  

Both. Similar to going to college. I know an Air Force lieutenant colonel who went to the Air Force Academy earn his masters degree entirely online while being in Afghanistan and other places in the Middle East. 

It’s mostly job training and lasts just 9.3 weeks. You won’t be able to take university classes full time while on active duty.

Anonymous, my comments are ghosted. But I have to study for the required knowledge before I go to boot camp.