Everything you say is right and sound until you invoke the economically meaningless distinction between employer and employee contributions to pensions.
Both percentages are fixed in contracts, so it matters not whether the total compensation package is, say $53,500 plus the cost of health insurance and other non-pension benefits, with the salary being $50,000 of which $1000 is required to be contributed to the pension and the extra $3,500 isn’t considered salary and goes to the pension, or the salary is $53,000 of which $4500 must be contributed to the pension, or the salary is $49,000 and there is a non-salary contribution of $4500 to the pension. The first you decry as the “teachers contribute almost nothing and the tax payers cover the rest,” in the second the teachers would be covering the whole cost of their pensions on your analysis, and in the last the taxpayers would be covering the whole thing on your analysis.
But this is a distinction without a difference. In each case the taxpayers are paying the teacher $53,500 for salary and pension (plus the cost of other benefits), of which $4500 is deferred compensation going into a pension plan. What is more, in each case, the pension contribution is non-taxable income, so in each case the teacher would get $49,000 in taxable income.
Which would be OK if they were consistently cranking out Einsteins and rocket surgeon graduates. As baby-sitters, it's about ten times what they're worth