ISS advised catering teams to place orders weeks in advance, postpone promotions and to remove unnecessary frozen items from the menu.
A spokesperson for ISS told ITV News: "We would like to reassure parents and carers that our ability to continue to provide nutritious school meals is not being impacted by the well-publicised shortages of items that the UK is currently experiencing.
"Naturally, we have contingency plans in place to ensure that a good supply of meals remains in place. That contingency planning includes regular communication with our stakeholders during these challenging times for many schools across the country.”
ISS says schools menus are being affected by a lack of staff, import delays and a shortage of lorry drivers.
Jacquie Blake, chair of LACA, also told ITV News: “There is no doubt that we are facing challenging times. Our food suppliers are under intense pressure, and our members are working hard to ensure that contingency plans are in place.
“Ensuring that children get a hot healthy school lunch has been and always will be our members number one priority. We are monitoring the situation carefully.”