Roads near Parliament were closed as protesters - including members of Save Our Schools West Sussex - marched from Whitehall Gardens to Parliament Square this afternoon (July 16).
For more than two years, headteachers have been campaigning for adequate money to enable them to run their schools five days a week, without cutting staff or the curriculum and without having to increase class sizes.
Despite government insistance education receives more money than ever, school leaders have warned that increasing pupil numbers coupled with a rise in expenses means they are actually worse off.
Mel Pickett, of Save Our Schools West Sussex said: "Our message to MPs is this funding crisis is the culmination of a lack of funding over a period of years and we really, really want our MPs to know that this process is not going away.
"Parents feel really strongly about this issue, the electorate feels really strongly about this issue and we implore our MPs to act now."
Most West Sussex MPs have supported the call for fairer funding.
In a letter to Justine Greening, secretary of state for education, all except Henry Smith (Crawley) and Nick Gibb (Bognor Regis/Littlehampton) called for amendments to be made to the new National Funding Formula as the proposed funding would not be enough to meet rising costs faced by schools.
Mr Gibb was unable to sign due to his position as minister for schools, while Mr Smith was serving as Ms Greening's parliamentary private secretary - a position he has since resigned.