It's also worth bearing in mind - for ATCOs and pilots who've been away from the training world for a while - that different schools may have different points by which a solo student MUST have a clear runway/clearance to land. For my own students it's 300' agl, not least because of the occasionally compromised climb performance of our training aircraft. It's not a committal height (we train them for go arounds right down to the flare!), but it is a point by which we would expect the student to be able to confidently continue the approach.