Now before faith came, we were imprisoned and guarded under the law until faith would be revealed. Therefore the law was our disciplinarian until Christ came, so that we might be justified by faith. But now that faith has come, we are no longer subject to a disciplinarian, for in Christ Jesus you are all children of God through faith. (Galatians 3: 23-26)

The Greek for imprisoned can also mean to protect or to keep under guard. The Greek translated as disciplinarian can also mean tutor.

It was the goal of the law to protect and preserve humanity, to prepare us in our role as children of God. With the arrival of Jesus the role of the tutor is no longer needed.

One translation renders verse 24 as, "Therefore the Law has become our tutor to lead us to Christ, so that we may be justified by faith." (Whole Bible)