George Budd from Moreton Hall, a boarding school near Oswestry, said staff, pupils and parents had been blindsided by the government's unwillingness to make a decision until the 11th hour with many schools having to go back in for a day before a return to online learning.
Many of his boarding pupils returned to Shropshire just hours before the 8pm announcement. Many of the UK students are now arranging to travel home again but others, including the international pupils, are to remain.
Moreton Hall has pupils ranging in age from four to 18.
"Over just a few days we have had the shambolic situation of the government threatening to take legal action if schools decided to close, to a move to a phased return, to the decision to close schools to all but vulnerable and key worker children," Mr Budd said.
"Our students were looking forward to returning to school and we have to remember that they are children and young people, not simply statistics. They and schools themselves are very resilient but these last minute changes are very difficult to take.
"I have talked to a lot of students over the last couple of days and they have an enormous mix of emotions that they are having to deal with. They need face to face engagement to learn the social skills and understand relationships."
Mr Budd said his school as all other secondary schools had spend a huge deal of time, effort and funds in setting up the testing centre on the site.
"Our staff have been trained, over the holidays, to carry out the tests and we had set the room up in readiness, only to be told on Monday night that the children would not be returning," he said.
"Now we are told that our teachers need regular testing, even though they are doing their on-line teaching from their homes, which could be an hour or more's drive away. If they drive in to be tested that is valuable teaching time that is being lost."
"Also we would have to keep some staff in school to carry out those tests."
The principal says he is also extremely concerned about the decision not to go ahead with exams this year.
"We all remember the exams fiasco and 'omnishambles' of last summer, has nothing been learned from that. To keep pupils motivated without exams at the end of the next two terms will be very difficult and our students are intrinsically very motivated and very driven."
"The decision has been taken so early, surely it would have been better to continue the online learning towards the goal of exams. Last year pupils had done their mocks and a lot of the course work so we had a lot of data to work with."
"This seems to be a knee-jerk reaction. there is enough time to consult with the various education bodies and come to a measured decision."