The Hansard Society, co-sponsor with the BBC's Newsround programme, said it was "disappointed". It aims to recruit two schools per constituency but three of the 10 Glasgow constituencies - Cathcart, Rutherglen and Baillieston - have yet to register. In six more, only one school has registered.
Across the country - as political analyst, Peter Snow might say - the picture is equally patchy with Caithness and Sutherland joining Falkirk West, Kirkcaldy, Dumbarton, Cunninghame South and Tweeddle in showing no interest.
This contrasts with the 1999 Scottish Parliament mock elections when schools in all parts were eager to cast their votes.
John McTaggart, principal teacher of modern studies at Boroughmuir High, Edinburgh, said the reticence was down to two factors: uncertainty about the election date and "Higher Still internal assessment fatigue".
Dr Rob Kerr, head of Peebles High, said the school's Scottish election had been "highly successful" but acknowledged staff pressures this time.
Dr John Halliday, head of the independent Rannoch School, was surprised to learn his was the only entry in North Tayside - the constituency of John Swinney, the SNP leader.