The union's executive council, meeting in Edinburgh at the weekend, attached significant preconditions to support for the reform. One of the key demands is that "the assessment burden on both candidates and teachers shall be no greater than the level currently obtaining in existing courses which are to be replaced".
The executive also endorsed ongoing criticisms about lack of resources, poor staff training and inadequate consultation.
The EIS insists that teachers' views on whether a school can adequately teach a Higher Still course or unit and whether the school has been properly resourced to do so "must be respected". Education authorities, which share many of the reservations, should enter negotiations with the unions, the position paper states.
There was no move to boycott the programme and a left-wing attempt by North Lanarkshire local association to remit the leadership's paper back for further consideration was the only one of five amendments to fall.
Fred Forrester, the EIS's depute general secretary, said: "There are very genuine professional and resource issues which the EIS will work actively to address. Our mood is not one of asking for the impossible to avoid implementing the programme, but it could turn in that direction if the problems are not resolved."
The Education Minister must make "a financial gesture to the teaching profession as an earnest of goodwill that can be measured not just in rhetoric but in hard cash",Mr Forrester said. If the issues were not addressed between now and the summer, the outlook for Higher Still was bleak.
Mr Forrester said that what he called "the fully monty" of Higher Still could not be achieved immediately. He has called for schools to be allowed to introduce the programme from August next year on a "self-phasing" basis in line with their own development plans. But he accepts that this could not apply to core subjects such as English.
The EIS is to seek another meeting with the two key players behind Higher Still, Douglas Osler, the senior chief inspector, and Philip Banks, chief inspector in charge of post-16 education. They met before Christmas and the EIS says pressure on the Scottish Office has forced assessment issues to the top of the agenda and won a number of concessions.
The union's position paper states: "We have obtained formal recognition that there is no official expectation that schools will introduce any units or courses other than those which replace their current provision. We have obtained formal recognition that school development planning should play a central role in the determination of progress in introducing further units and courses into a school's provision."