Hawick High missed two penalties in the closing stages of their quarter-final at Mansfield Park and Marr held on for a 15-14 victory. The Troon side face another long journey for their semi-final, to Morayshire to play Gordonstoun, who were 27-10 quarter-final victors over Culloden Academy.
Marr beat Kelvinside in a tight semi-final last season and the pair could meet in the final this time around. Kelvinside were 63-0 quarter-final winners against Queen Victoria School, and will be away to Glenalmond College in the semi-final, the Perthshire school having reached the last four with a 39-19 victory over Royal High.
Three independent schools in the semi-finals of the plate is an indication that certain schools in the private sector are choosing carefully the level of competition at which they enter. The cup has become essentially for a small group of elite rugby-playing schools who have now, through sports scholarships, intensive coaching and harder matches often with schools from south of the border, drawn away from the rest of the pack.
How to make the cup accessible to a wider group seems to be on the agenda for raising the standard of state school rugby as outlined by the Scottish Rugby Union in their overall plan to improve rugby in Scotland. Any attempt to turn the clock back to a time when state school rugby was healthy will be a formidable task.
At least the SRU can trumpet success with its Schools of Rugby scheme, the best example of which is Carrick Academy, who reached the final of the plate two seasons ago. Gordon Brown, a driving force for rugby at Carrick, said: "Without the School of Rugby scheme we wouldn't have been able to give our teams dedicated periods of rugby in their timetable."
One idea being floated to make the cup more accessible is to extend the notion of 'composite' sides to district teams, so that, for example, a Glasgow state schools side, or a Borders schools side, could enter the cup, with the proviso that these regional sides had the opportunity to play warm-up games against the leading private schools teams.
Before their semi-final, Kelvinside lost 20-16 to Glasgow Academy, who face Marr College this weekend. Marr, who also play Glasgow Academy in Troon next Saturday, continued their fine run this season with a 21-19 win over St Columba's.
Elsewhere, George Watson's College were 17-14 victors over Merchiston, Stewart's-Melville College won 22-3 against Dundee High at Inverleith; Edinburgh Academy were 29-17 winners over Glasgow High; and George Heriot's beat St Aloysius College 19-17.