There is something strange about this. If he was head hunted the new company would require his services and would probably have asked him to complete an application form which would normally ask for educational qualifications at that stage, not after the employee has started employment. Was it a requirement of the job that the applicant must have three A levels grade A to C?
It is not unknown, I do not say it happened in this case, that a successful person in a rival organisation is offered a job and then dismissed to remove them from the market. But I would not expect any responsible organisation to act in this way. There is little remedy as the person involved does not have the qualifying period of service to make a claim to an employment tribunal and the no qualifying period gives very restricted reasons. The new employer would probably claim the dismissal under capability or qualification, which is one of the five potentially, fair reasons for dismissal even with the correct qualifying period.