Stop teaching content
Whatever has not been learned by six weeks out is not going to be learned in a form that survives a timed section. New material this late competes with the material that was already solid, and the solid material is what loses.
Buy timing instead
Most of the recoverable points in the last six weeks are pacing. Two full timed sections a week will find more marks than twenty hours of content review, and they find them in the first fortnight.
Three question types, no more
Pick the three costing the most marks and work only those. A student who fixes three types moves further than one who reviewed everything, because reviewing everything is how you spend six weeks confirming what you already knew.
One whole Saturday morning
At least one full sitting at the real start time, in a room that is not their bedroom. Stamina is a skill, and it is the only one on this list that cannot be practised in an hour.