The achievement follows their months of hard work promoting equality and diversity to the school community.
Youngsters started training sessions for staff and also began a weekly diversity group to provide a safe space for students.
Head teacher Stephen Miller said: “We are immensely proud that our work on LGBT issues has been recognised in this way.
“We have demonstrated in a very clear way that each pupil has a unique value and that no-one should be subject to any factor as a definition of who they are as a person.”
The LGBT Youth Scotland’s School Charter awards help schools look at their policy and practice in the context of LGBT diversity.
Falkirk Councillor Adanna McCue, spokesperson for education, said: “We are especially proud of Denny High.
“We hope other high schools throughout the Falkirk Council area will take part in the Charter Mark in the future.”