The Sun says an agreement worth £2.5m was close with Chelsea but Tisdale refused to give any hints about the 16-year-old's next destination.
Tisdale told the Express and Echo: "He's got to concentrate this year on his GCSEs – he's a member of our first-team, and any business that Exeter City decide to do will not be conducted in the press.
"At this stage, he belongs to Exeter City.
"We continue to produce with frequency players who are technically able.
"It increases all the time and the basic ability levels of players is rising all the time.
"It's to the credit of Simon Hayward and the academy set up and the coaches who work with him."