There is a limit of 200 students per account whether it is the free Lite or paid Teacher Deluxe version.
For both the free Lite or paid Teacher Deluxe versions, you can have up to 200 students in a single account before the system won’t allow you to add any more students. You will not lose any data. The system will just not permit the addition of any more students once the 200 students total has been reached unless some are removed.
Single accounts needing to manage more than 200 students should consider getting a district account where numbers are not limited and large scale management and access of data is accommodated.