The primary purpose of an apprenticeship is the training of the apprentice. Apprentices are considered to be employees from the day their apprenticeship starts. Once the apprenticeship comes to an end, the apprenticeship contract will sometimes also end.
If the apprentice was not previously an employee and continues with the employer after they complete their apprenticeship, they would normally expect to sign a new contract.
For new employees, the employer can add a probationary period, but needs to be aware that for their first 12 weeks on PAYE, the apprentice will be in full-time training.
In addition to your usual contract wording, appropriate wording for an apprentice contract might look something like this:
You are employed as an apprentice and your employment may terminate upon completion of your apprenticeship.
Apprenticeship start date: <start date of employment> Your estimated completion of learning date is: <21 months later>
Apprenticeship standard and level: Software Developer, Level 4