Here's what we can speculate:
* He probably married Anne Hathaway: Records show he married at 18, but it's possible they had a secret marriage when he was 15.
* He might have started an apprenticeship: In that era, boys often began apprenticeships around age 14. This could have been in his father's trade (glover) or something else.
* He was likely learning to read and write: While not universal, literacy was becoming more common in Shakespeare's time.
* He could have been working on the family farm: His family owned land, and he might have helped with agricultural work.
In short: There's no definitive answer. We know little about Shakespeare's life before his theatrical career began.