Morgan Sindall will start work at Bellerive FCJ College in Princes Park in February to create a new £5.6m teaching and sixth form building which will be completed in early 2016.
At St Francis Xavier’s in Woolton Kier will carry out a £7.6m contract to create a brand new science block and sports hall.
Work is due to be completed by November 2015.
Mayor of Liverpool Joe Anderson said: “This is a much-needed investment in two of our schools and is part of my commitment to deliver at least 12 new schools for pupils in the city.
“We are working with construction firms to make sure as much of the money is spent locally as possible and benefits the workforce in the city.”
At Bellerive, 70% of the subcontracting work is expected to be by Liverpool firms, with another 15 percent from across the city region. Eight apprenticeships will be created.
A target has been set for 85% of the subcontracting work at St Francis Xavier’s to be carried out by Liverpool firms, with another 10 percent from across the city region. Nine apprentices will be hired.
The work forms part of the £169 million Liverpool Schools Investment Programme, devised as a rescue package following the scrapping of Wave Six of Liverpool’s Building Schools for the Future (BSF) project.