CCF cadets did GS on continuous courses - mostly, our local VGS let us take up any slack in weekend courses where possible. The issue was that any CCF cadet selected for AGT would time out before they were qualified to instruct. In 14 years I've only had one selected, and as a boarder he had to turn it down as he didn't live close enough to get there in the holidays (and had school on Saturdays).
With CEP more CCF cadets will be in state day schools and if they live close enough then this might be a realistic option, but they'd have to join the ATC when they left school so they might as well join now...