I wasn't able to find whether there actually is a program to learn this one particular skill without having to be enrolled for the full school year.
A welding certification takes a while. In the US, at least, once you make that weld you own it for life. If a natural gas main bursts 40 years from now at the joint you welded, it's your fault.
There's a big difference between "we went to Harbor Freight so that inner city kids could weld old car parts together to make public art" and "we're training people to make a living."