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About STACK

STACK is an online assessment system for mathematics and STEM, designed to enable students to answer questions with a mathematical expression, such as a polynomial, or with free-text input.

A STACK question giving specific feedback on a partially correct answer, including graphing the student's answer.
STACK helps students learn from their mistakes through specific feedback.

Computer Algebra Support

STACK uses the Computer Algebra System Maxima to evaluate expressions.

  • Mathematical answers: questions are not limited to multiple choice.
  • Randomise questions: so different students see different variants of a quiz.
  • Graphical support: make your questions stand out by integrating Maxima plots or JSXGraphs

Validation of answers

Before answers are graded, students confirm their answer is interpreted correctly by the system. Invalid answers, like ones with mismatched brackets, are rejected.

  • Fair: students are not penalised for poor computer skills.
  • Flexible: the teacher decides what a valid answer looks like.

Intelligent marking

Teachers write grading trees that mark answers based on mathematical properties, like "is it factored?"

  • Objective and transparent algorithms provide reliable assessment.
  • Specific feedback tailored to each student's answer.
  • Multipart questions with follow-through marking.
  • Give-example style questions with many correct answers.
  • Diverse question types involving free-text, scientific units, numerical accuracy, line-by-line reasoning and more.

Free-text input

STACK allows students to enter free-text answers, representing their complete argument.

A free-text input STACK question.
STACK helps students represent their complete mathematical argument.

STACK combines the best of traditional online assessment with contemporary digital documents.

  • Accessible digital documents allow students to represent their answers simply.
  • Teachers can extract features of students' answers to automatically assess.
  • Objective and transparent algorithms provide reliable assessment.
  • Specific feedback tailored to each student's answer.

Open-source

As an open-source project, users help improve STACK by adding features, translations, bug reports and more. Many users share STACK materials, for example through the ABACUS material bank.
Credits and contributionsABACUS material bank

Trusted user base

STACK is trusted by many respected institutions.

Commercial partners

STACK is trusted by a number of commercial partners.