I am unsure on the academic question - do rankers need a-levels. I think, but am not 100% sure, that I did put one through the system without. He had the nouse and could have done A-levels, but didn't. I also had a couple that had degrees and pretended not to want "the responsibility" when they joined.
Going outside your chain of command as Dragstrip infers may not be 100% wise - apart from hacking them off and potentially losing their (perhaps valuable) recommendation/backing, you may not be given time to attend the required selection procedures...
I have put maybe 5 or 6 into the commissioning system from the ranks and have only once had a soldier that then had second thoughts and therefore got an "at risk" recommendation from the CO. I am pretty sure that if you are to join from the ranks you SHOULD receive their recommendation as it is all on the forms you need to complete.