Questions texted to 82ASK by students include "What do semi-colons do?", "How can I cheat without getting caught?" and "How do I get to the exam hall?"
The service for GCSE, A-level and university students, launched last August, deals with tens of thousands of the pound;1 texts a month and promises to reply to 89 per cent of them within five minutes.
Sarah McVittie and Thomas Roberts, the co-founders of 82ASK, are to approach schools to promote the service after noticing that students' calls doubled at exam time.
Mr Roberts, 27, an Oxford theology and philosophy graduate, said: "Most calls come from maths and physics students. But you get all sorts of questions. Someone asked how much wheat there was in a potato."
Questions are answered by 35 so-called Texperts, working from home. Of these, 89 per cent are graduates, a third from Oxbridge.
Miss McVittie, a 27-year-old Chinese and economics graduate, said: "Pupils ask for emotional support, too. They want to know how to calm their nerves.
We use a number of different resources and offer the same advice as exam boards."
Students seeking tips on how to cheat are told: "Not easy, always a risk.
Exam board spokesman: we trained examiners to find evidence of cheating.
We're clear that those who cheat will be caught and punished."
TES readers can get a free text by including the code TES1 in their question to 82ASK82275.