subjunctive followed by indicative
I would go with one of two sentences, but mixing the two like this isn't correct. Either:
"If all the schools were to implement this program, which now exists only in the lower grades, then five years from now we would not have parents complaining that their teen-aged children still can't read."
Or: "If all the schools implement this program, which now exists only in the lower grades, then five years from now we will not have parents complaining that their teen-aged children still can't read." (remove were to)