The city school head to Rugby School (Wednesday, July 8) where they will take on 19 other schools from across the country, including Burraton Primary from Saltash.
The two finalists from next week's event will have the honour of playing each other at Twickenham as a curtain-raiser to England's match against New Zealand on November 21.
Widey Court booked their place in the National Finals by winning the West Devon Primary Schools' Tag Rugby Festival at Marjon before triumphing at the regional South West Championships at Taunton School, where Burraton finished runners-up.
Team coach Shaun Boyle said his team can be proud of their achievements so far.
But he is hoping they can put on a good show next week against the top tag rugby teams in England.
"The team have done really well to reach the National Finals," said Boyle.
"But I know they are determined to do well next week and try and make their way to Twickenham.
"It won't be easy against some other top schools from across the country, but this is a good side.
"There are no real stars, but just a bunch of players who work together as a team.
"There is a superb team-spirit and we are hoping that it will help us do well next week."
Boyle thanked the financial contributions from Plymouth's School Sport Co-ordinators Scheme, construction company Devon Contractors and Widey Court's Parents, Teachers and Friends Association in enabling the team to make their trip to Rugby School.