Digital Red Pen was built by a working math teacher for his own grading load — and refined
across five periods of Algebra 2 in his own classroom before any other teacher was asked to
trust it with real grades. Co-founders: Zack Alexander, a veteran K–12 educator, and
Dr. Lara Krisst, a cognitive neuroscientist at Caltech.
About Digital Red Pen
Who built it
and why.
A working math teacher's grading problem. A tool that reads the work while the teacher
rules on every call. Built and tested before it was ever shown to anyone else.
A grading problem lived every weekend.
Zack Alexander taught secondary math for years. After the exams were over — after the
lessons, the planning, the classroom — there was still the stack. A hundred sixty handwritten
exams, each with partial work, scratch-outs, and the specific wrong turn a student made at
step two. The kind of stack you can't responsibly mark in a Saturday afternoon without losing
the signal.
The tools that existed didn't help. Bubble-sheet scanners score only right-or-wrong final
answers. Gradescope groups similar answers so the teacher grades faster — but the teacher
is still the one grading. What Zack wanted was a tool that reads the student's actual
handwritten steps and awards partial credit from the process shown — the way a careful
teacher does — so he could review the results and make the calls instead of marking
every paper from scratch.
He built it for himself. Then he ran it on his own classes — five periods of Algebra 2,
over a semester — before he asked anyone else to rely on it. That is the product you
see here.
Before we asked any other teacher to trust it
"Built and refined by its co-founder across five periods of Algebra 2 in his own classroom,
over a semester, before we asked any other teacher to trust it with real grades."
The founders
Zack Alexander
Co-founder
A veteran K–12 educator and former high-school math department head who has taught in
both public and private schools, and a summa cum laude graduate of UC Berkeley. He built
Digital Red Pen for his own grading load — and refined it across five periods of Algebra 2
in his own classroom before opening it to other teachers.
Dr. Lara Krisst
Co-founder
A cognitive neuroscientist at Caltech, she grounds Digital Red Pen in how people actually
perceive and reason about their work.
Frequently asked questions
Who founded Digital Red Pen?
Digital Red Pen was co-founded by Zack Alexander, a veteran K–12 educator and former high-school math department head, and Dr. Lara Krisst, a cognitive neuroscientist at Caltech. Zack built the tool for his own grading load and refined it in his own classroom before opening it to other teachers.
Was Digital Red Pen tested in a real classroom before launch?
Yes. The tool was built and refined by its co-founder across five periods of Algebra 2 in his own classroom, over a semester, before it was offered to any other teacher. No other teacher was asked to trust it with real grades until it had been through that refinement.
What does Dr. Lara Krisst contribute to Digital Red Pen?
Dr. Krisst is a cognitive neuroscientist at Caltech. She grounds Digital Red Pen in how people actually perceive and reason about their work, bringing academic rigor to the quality and design of the feedback the system produces.
Why did a math teacher build a grading tool?
Zack Alexander built Digital Red Pen for his own grading load — the Sunday-night stack of handwritten exams that was the cost of teaching math well. The goal was a tool that reads the student's actual work and awards partial credit from the steps shown, while keeping the teacher in the judge role for every call.