Catch up quick: Differences between Johnson and the board emerged during CPS' budget process in July when the board defied the mayor's directive to take out a high-interest loan to cover non-teacher pensions and the new Chicago Teachers Union contract. • Tensions heated up more recently as CPS CEO Pedro Martinez claimed the mayor asked for his resignation — a contention the mayor disputed this week — but the board, which controls the CEO's fate, chose not to fire Martinez. What they're saying:...