I have had c# training, but never had the opportunity to put it to use. Starting in high school I learned BASIC, COBOL, ALGOL, Focal, FORTRAN. Moving on to college I learned Pascal, Modula-2, Ada, VAX and PDP-11 Assembler, and more COBOL. In the real world, the only language I used directly that I learned in school was COBOL. Learned and used several reporting tools, scripted several Spreadsheet applications, and did a lot of command line scripting for several OS's.

Is learning C necessary, I don't thnik so. Learning to convert algorithms into working code, yes.

Learning to write well performing code, that comes with experience and mentoring. Not really sure that can be taught in school.