Angry demonstrations are expected in Riga tonight over a controversial new education Act set to become law in September that stipulates Latvian as the key language of instruction in schools.

The law is opposed by the Baltic state’s large Russian minority and has split the country’s parliament.

Education minister Karlis Sadurskis is on record as threatening to sack the heads and staff of those Russian schools which support mass protests. The EU, which Latvia joins tomorrow, has said the language laws conform to European minority rights standards.

Some 2,000 Russian schoolchildren demonstrated against the new law outside the presidential palace recently, chanting “no to the reform” and carrying placards reading “Russian schools forever!” and “Hands off Russian schools!” It was the fourth such protest this year.

The education reform, passed in February, says that at least 60 per cent of classes in state schools, even those catering to the large Russian-speaking minority, must be taught in Latvian from September.

Partly to counterbalance the dominance of Russian in many areas during decades of rule by Moscow, the Baltic state declared Latvian the sole official language in 1999, eight years after it regained independence amid the collapse of the Soviet Union.

The issue has polarised politics and increased tensions in the capital, Riga, where half the population is Russian.

Ethnic Russians - many of whom are second or even third-generation Latvian-born - fear the move to Latvian-only teaching will put their children at a disadvantage and fuel ethnic conflict.

However, Latvians counter that the measure is meant to help integrate minorities, adding that those who do not learn Latvian will find it hard to secure good jobs.