No country can reduce the number of people who attend universities from the top down, without suffering serious social backlash. People see higher education as a gateway to a better life, and a prerequisite for marriage, you cannot deprive them of that right just because there are more graduates than you want.
There has to be either incentives or promotions of vocational trades. Your talking about a country
where there is a huge stigma against people that don't attend university. You have to undue that mentality first. Then people would voluntarily see other paths as viable alternatives to universities.
But a better solution that I believe in is the expansion of the Iranian market to be able to absorb the graduates. Already we are seeing the growth of Iranian influence in Syria and the next elections in Iraq will likely be an increase to Iranian political presence in that country. If Iran expands to the markets of its surrounding neighbors, it will reap the benefits of having a determined and driven people, who attend universities at such a high rate.