The EIS, as Scotland's dominant classroom union, is a key partner in the consensus politics that have transformed the educational sector. Five years ago, the more radical left-wing elements were queueing up to decry the post-McCrone agreement. Now the EIS is strident in its defence in the wake of media claims that teachers have not delivered their part of the bargain.
Will its members go on strike in pursuit of class size maxima of 20 pupils across the board? Unlikely. The Scottish Executive's Labour-Liberal Democrat partnership implicitly endorsed the argument that smaller class sizes can raise attainment when it set limits of 20 for maths and English in S1-S2, and 25 for P. The hard fact is that few schools have the capacity to deliver classes of 20 for every subject, and the EIS knows it.
The vote to ballot members on industrial action if the executive does not match its aspirations is therefore a bargaining chip as the Scottish parliamentary elections approach. The EIS has 58,000 members and each party will be hoping to woo the teacher vote next May.