"The computer and teacher sets the task and you can't move up through the levels until you've mastered a lesson, and you can do it at home."
Mr Nelson said teacher Willy Jephson had embraced the Khan Academy programme, which was vital to its success, and within the structure of the scheme was able to track class progress as a whole as well as focus on each of the participants.
"When the teacher's on board it can work incredibly well. I just love it and apparently so do the kids."
Khan Academy is a non-profit educational website created in 2006 by educator Salman Khan to provide "a free, world-class education for anyone, anywhere", according to Wikipedia.
In late 2004, Khan began tutoring his cousin in mathematics using a notepad.
When other relatives and friends sought similar help, he decided it would be more practical to distribute the tutorials on YouTube.
Their popularity there and the testimonials of appreciative students prompted Khan to quit his job as a hedge fund analyst and focus on the tutorials full time.
The Khan Academy scheme is open to each of the 87 pupils enrolled at St Mary's School, Mr Nelson said, although only the single class is at present engaged on the scheme in classroom hours.
Mr Nelson hoped the programme would expand to include every class, depending on the enthusiasm of teachers for the scheme.
Mr Jephson said keeping in step with the programme was comprehensive and precise, and allowed each child to learn at his or her own pace and particular level, while lessons could be enhanced or accelerated for each as needed.
"It's easily managed and all your energy goes where it's needed. It's perfect," he said.