The ASTI says there should be allowances for vulnerable teachers under the new restrictions.
Cabinet Ministers have been meeting to sign off on the highest level of restrictions for a six-week period.
It is expected that schools will be allowed to stay open under Level 5.
The secondary teachers' union says 800 of its members who have underlying health conditions applied to work remotely over fears of contracting the virus.
President of the ASTI, Ann Piggot, says the union's members are questioning why are their lives are not valued as much as others.
Speaking on The Hard Shoulder, Ms Piggot said that there is confusion over what Level 5 means for schools under the Government's Living with COVID plan.
She said: "At Level 5, it says the recommendations are based on situational evidence at the time, and we're not really sure what that means.
"Does that mean collectively a decision will be made on all schools, or will it be made on individual schools depending on the number of cases?
"The ASTI will not be making that decision, it's the Government making that decision.
"What the ASTI is pushing for is adequate health and safety at all levels in our schools and if we're at Level 5 where everything is closing, our members are wondering why are their lives are not valued as much as others."
Under the new restrictions, construction sites will stay open as will essential retail outlets, while pubs and restaurants will move to takeaway only.
Ms Piggot said: "Teachers are going into work with 30 people in front of them and then collectively during the day they're meeting up to 200 students
"In an area where students are outside at lunchtime not wearing masks, we want social distancing and efforts are being made to have that in all schools.
"So there are certainly problems for teachers that other workers don't face.
She said that 800 high-risk teachers had applied to work remotely but they hadn't been permitted, while ther teachers are worried about going home to vulnerable people in their household
Ms Piggot added: "Definitely for the high-risk teachers, they certainly should be allowed to work from home or in schools with certain restrictions on them where they wouldn't be inside facing a class of that number, maybe in smaller classes or maybe to teach remotely in some way."
She said the ASTI is hoping to engage with the Department of Education and the Minister on those issues.
She added: "I think the biggest issue for members is going into a school, knowing people have tested positive, not being told whether it's one or five or ten, worried that you're in a room where somebody might be positive.
"The tracing is very slow, the testing is very slow depending on the area."
Ms Piggot said: "The thing is, if this virus is in schools, it's going to go back into the community.
"If you're going to impose such severe restrictions on people, will keeping schools open negate that or will it make any difference?"