DeltaMath: An Innovative Website for Student Practice

One of the most difficult things for math teachers to do when writing lessons is finding enough time for students to practice skills. Many web sites, including Carnegie Learning (, Castle Learning (, and Learner Pal (, provide online resources to help teachers create additional practice for students. Like these sites, Delta Math ( also allows teachers to create automatically graded student assignments, but it has several innovative features that make it more powerful and useful than its competitors.

DeltaMath was founded by Zach Korzyk (@MrDeltaMath), a New York City public school math teacher and Math for America Master Teacher who created the site as an online tool to help his 11th-grade students learn problems. The site has since evolved into a resource of problems for levels ranging from middle school to calculus as well as a separate section for computer science.

I have used DeltaMath in my high school math classes for several months. In a future blog post, I will describe some of the ways that I have used this site to improve both my instruction and my students’ performance. This article describes DeltaMath’s features and limitations.

Easy Setup

Both teachers and students can create DeltaMath accounts after entering basic information. Teachers provide their name, email address, and school. Student information cannot be uploaded from a separate file, so each student account must be created individually using a student’s name and email address. Each teacher gets a unique six-digit identification code that can then be shared with students who want to be added to a teacher’s class.  To be added to a teacher’s roster, students must know their teacher’s identification code.

After logging into DeltaMath, teachers are taken to a screen that lists all of the available topics. Topics are grouped by level (Middle School, Algebra I, Geometry, Algebra II, Pre-Calculus, Calculus, and Computer Science) and then by unit. Three drop-down menus at the top of the page provide access to DeltaMath’s functions. You can monitor student performance, create or edit student assignments, or access several management tools.

Amazingly, all of this is accessible for free, although DeltaMath welcomes donations via PayPal.

Customized Practice

DeltaMath creates unique assignments for each student (while each student assignment has the same topics, the question that each student sees has different numbers). Unlike other sites, which have a limited number of questions on each topic, often taken from previously published New York State Regents exams, DeltaMath has hundreds of similar questions for each topic.

To create a student assignment, teachers select “Create Standard Assignment” from the Create/Edit menu. Teachers then name the assignment, add specific skills, set due dates and times (with the option to set late dates with a specified percentage penalty), set a date and time when the assignment is visible to students, and set which classes get each assignment. Teachers can also modify an existing assignment. Teachers or copy another assignment, either from themselves or from other teachers (with the other teacher’s permission, of course).

Teachers get access to all of DeltaMath’s questions and can add questions from any topic to any assignment. Thus, an Algebra II assignment could contain questions from Algebra I or even middle school. Many topics are separated into levels of difficulty. For each topic, teachers can see a sample question and its solution. Each topic covers a specific skill, allowing teachers to focus on specific skills. (For example, there are 23 topics just on factoring alone.) Teachers can also create assignments that provide a random mix of questions on various topics.

DeltaMath also provides support for students who need help. Before typing in an answer, students may click a button to see a similar example with a complete solution. (Teachers may choose to disable this feature if desired.) After students enter an answer, DeltaMath tells them whether or not they are correct, showing a complete step-by-step solution.  Most steps in the solution include a brief explanation, such as “Take the log of both sides.”

Teachers can customize the amount of practice students can on each topic by specifying how many questions a student must get correct on a topic. If a student gets a question incorrect, the student’s score on that topic (which can never be negative) decreases by a teacher-specified amount ranging from 0 to 5 points (the score can also be set to go down to 0) and the student must answer more questions on that topic to move on. This penalty feature essentially allows students to continue answering questions on a topic until a teacher feels that they can move on. Since each DeltaMath question has a unique answer, students cannot cycle through all of the questions on a topic, view their answers, and enter the answers when the questions reappear. This significantly reduces cheating and enables students to practice authentically instead of redoing the same questions.

In addition to generating unique problems for each student, DeltaMath provides other tools to prevent cheating. It can generate a unique code for each problem that teachers can require students to copy with their work and submit for inspection. An IP address analyzer identifies instances where multiple accounts are logging in from the same Internet address – a potential indicator that one student is doing homework for several others.

Monitoring and Managing Students

DeltaMath gives teachers many ways to monitor and analyze student work. Teachers can view a spreadsheet-like grid that shows each student’s grade on each assignment. By clicking on a student’s name in this grid, teachers can also see how many questions a student answered on each topic, whether or not the student answered it correctly, what answer the student typed, and how much time the student spent on each question. Teachers can also export grades from selected assignments into a .csv file, which can be opened by spreadsheet applications like Microsoft Excel or Google Sheets.

Two other features allow teachers to track student work in other ways. The Problem Logs feature allows teachers to see the problems that students did most recently in chronological order. This is especially useful for teachers who are supervising student DeltaMath work in class. The Student Last Action feature allows teachers to see the last date and time that a student did something on DeltaMath.

DeltaMath has several tools that help teachers manage student accounts. Once a student’s account is created, a teacher can add the student to one or more classes. This is important since teachers give assignments only to one or more classes, not to groups of students. Teachers can add or delete students to a class after the class is created and can even release them at the end of the school year so they can join another teacher’s class next year. Unfortunately, the one part of a student account that neither a teacher nor a student can change is the email address, which is tied to the student’s account. If a student mistypes an email address or wants to change an email address, the student must create a new email account but would lose all of the data tied to the previous account.


DeltaMath has a few limitations.

As with other web sites that grade student responses automatically, the site’s questions are multiple-choice or short-answer. Longer constructed response questions, such as geometric proofs, are not available, but no online tool can realistically assess such questions. (A web site that could generate hundreds of proofs of similar difficulty and grade student responses would be an impressive feat of artificial intelligence!)

Students must type in a correctly formatted mathematical expression (an on-screen keyboard allows students to type in mathematical symbols) or select from a drop-down menu. Some of my students have expressed frustration that they all of the work correctly but failed to enter the answer in the format required by DeltaMath. A brief hint reminding students of the proper format for certain questions might be helpful. Also, there is no detailed written help for teachers. (Fortunately, most of DeltaMath’s features are fairly self-explanatory, and the site’s online videos cover most of the site’s features.)

Since each class can be linked to only one teacher, then co-teachers of a class must come up with creative ways to share students. One workaround is to create a separate teacher account with a different email address and password for two teachers to share. Teachers can share assignments by entering another teacher’s unique identification code.

The site does not allow teachers to add their own topics, questions, or explanations. (Of course, students could also search for additional help on their own.) I have found that some of my students appreciate having a method that differs from what I taught in class, while others get confused between the two methods. Teachers who use DeltaMath should look at how the site presents topics and can either adjust their instruction or tell students that DeltaMath presents an alternate method.

While DeltaMath has extensive Algebra I and Algebra II problems, including many that are no longer covered in the Common Core Algebra I/Geometry/Algebra II sequence (such as solving trigonometric equations), it has less thorough coverage of high school Geometry.  When I taught Geometry, I often had to supplement DeltaMath with other assignments.


DeltaMath is an incredibly powerful instructional tool. Despite its relatively minor limitations, it is the best site that I have found that gives students the ability to practice independently while giving them instant feedback on their work. Unlike other online tools designed by former educators or people with limited classroom experience, this site is designed by a math teacher who uses it with his students. The site is constantly improving, with more features and topics added every few months. Best of all, DeltaMath is free. What DeltaMath does, it does well – generally better than sites costing hundreds or thousands of dollars more. If you teach middle school or high school math and you’re not using DeltaMath, you should take a serious look at it. It will probably change the way that you teach.

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