*The usual interpretation is
that in order to direct and supervise, the glider must remain within
visual range of the airport.

Personally, I don't interpret it to mean that at all. The student
must be authorized by an instructor before the flight to undertake
certain teaching points while solo. One such teaching point could be
navigation and the student could be authorized to do their 50 km
flight if the instructor deems the student capable. In fact, in the
power private license standard, a solo cross-country flight is
required. This flight takes the solo student to two different
airports and covers somewhere around 250 miles.

Back to the original question:

At my club, students do not typically fly solo cross-country and like
all other club pilots, who are not checked out for cross-country, they
must remain within glide distance to return to the traffic pattern at
the appropriate height and location. Any abbreviated circuit as a
result of too low an arrival becomes a de-briefing and teaching
point. We do not have any specific landmarks or area they are
required to stay within, but on certain days (windy, poor visibility)
and with some students the instructor who is supervising the flight
may provide specific instructions as to where the student is expected
to be. In al other cases, the students are expected to use their own
judgement.

A student who lands out is not sanctioned, it is again a teaching
point. The decision to land was likely the best decision they made in
the flight. The question becomes what decisions put them in the
position where they had to make the final land out decision. That is
what need correcting.

Cross-country in club ships requires the pilot to be signed out in
each specific type they want to fly cross-country. The checkout
involves, first having completed the requirements of the bronze
badge. Subsequent requirements include three consecutive spot/
precision/short landings on type. Full briefing on controlled
airspace and radio procedures (followed by written test - new this
year). Other requirements include:
• Minimum of five flights on type.
• Demonstrate ability to rig and derig glider.
• Ability to organize a retrieve crew.

As part of the Bronze badge training, all students are required to
navigate to a neighbouring airport about 10 miles away, plan a circuit
and land there. This also requires an understanding of glide
calculations to determine what departure height is required to arrive
at the other airport around 1500 AGL. The flight back, also focuses
on navigation and glide calculations to arrive home at an appropriate
altitude.