More than 1,700 school cleaners, janitors and support staff say they do not feel safe at work and are being put at risk every day.
In an open letter to Nicola Sturgeon, the GMB union has raised concerns over PPE and risk assessments.
Schools are set to return in August with no social distancing in place if coronavirus is suppressed adequately.
The Scottish government said workers should have access to PPE where necessary.
A spokesman said there should be "appropriate hygiene facilities" and any wider support that staff need.
The letter, which will be handed in to the Scottish Parliament later, says the workers were being given the "bare minimum" of PPE (personal protective equipment) and many of them only had access to hand-washing facilities
"We do not feel safe at work and we are being put at risk every day," the letter says.
This letter is signed by staff who call themselves "the workforce that seems to have been forgotten".
They said they had been working throughout lockdown in school hubs and were now worried because guidelines for site-specific risk assessments were not being carried out and some staff did not have the PPE they needed to feel safe.
They said the guidance, to keep their members who work in schools safe, must be revised and must be more robust.
"We have continued to look after the children of other key workers and vulnerable children, have continued to feed them and provide personal care, cleaned up after them and made sure their environment is nurturing and safety," the letter says. "We have done this with love and with little regard for our own health and safety.
"Your government's guidelines are very clear in that a full individual risk assessment should be carried out before any staff and pupils return. We are the staff working in and opening up schools, and we need you as our first minister to enforce these guidelines."
They also said they did not feel safe using public transport to get to and from work.
They also highlighted the fact that due to cuts to cleaning budgets and staffing, many of them had multiple contracts or were required to move between buildings throughout the day.
"Our families are being put at risk. We are scared to take the virus home," the letter said.
"Some of our colleagues have been very sick and some have died. Without proper protections and investment now, more of us will catch this virus and more of us could die."
They called for investment for local authorities to be used for:
- Individual school risk assessments that staff can access without having to ask
- Personal Protective Equipment (PPE)
- Investment in bereavement and mental health services that can be urgently accessed
- Better contracts
- Increased cleaning hours
- £2 an hour wage uplift
- Robust national guidance
A Scottish government spokesman said: "Our hard-working school staff continue to provide an invaluable service in the hubs and we owe them a huge debt of gratitude.
"Everyone has a right to feel safe at work and we have been clear with local authorities that workers should have appropriate hygiene facilities and, where necessary, access to PPE and any wider support they need.
"The health and wellbeing of pupils and staff continues to be our priority as we plan for the safe reopening of schools in August. The plan is conditional on infection rates being low enough to continue to suppress the virus, and appropriate public health and protective measures being in place."
Schools had originally been preparing to return with a "blended" model of face-to-face teaching and home learning.
But last week, Education Secretary John Swinney said "significant progress" had been made in controlling the spread of the virus so ministers were now preparing for all schools to open full-time in August.
He said blended learning may still have to be implemented if infection rates rise again, warning that "there are no certainties with this virus".