Rallies and ceremonies will be held across Russia for three days to commemorate the first anniversary of the tragedy, in which 331 people died, 186 of them children, in the school in North Ossetia, in the Caucasus region, where three days of official mourning have been declared.
Angry mothers are also planning to stage a face-to-face meeting at the Kremlin with Russian President Vladimir Putin.
The bells tolled at 9.15am local time, followed by the music of Mozart’s Requiem at the site of the attack.
Hundreds of victims’ family members came to place flowers and candles in the ruins of the school’s gymnasium, where the hostages were holed up for three days.
Streets around the school have been cordoned off and metal detectors erected outside the school grounds.
Photographs of the 318 hostages who died have been posted on the walls of the gymnasium, and the school’s walls have been draped in red cloth decorated with white doves.
Schools across Russia have started the academic year with a minute’s silence for those who at the hands of Chechen militants, and security was stepped up at schools ahead of the anniversary.
Ten Russian servicemen, two rescue workers and 31 of the hostage-takers were also killed in the climax to the crisis on September 3, as security forces battled the hostage-takers.
The Committee of Mothers of Beslan said it has secured a meeting with Mr Putin in Moscow.
The mothers are expected to express anger towards the leader, saying he and other top officials must bear responsibility for what happened in Beslan.
Opposition parties and human rights campaigners will on Friday also hold a memorial ceremony in Moscow to condemn the conduct of Russia’s anti-terrorism campaign and demand a more thorough investigation into Beslan.
The one-year commemorations have been marked by increasing expressions of public anger at the authorities’ handling of the Beslan crisis.
Many people in Beslan remain in deep mourning and are demanding to know why so many gunmen were able to enter the school grounds and why officials refused to negotiate with them.
Some mothers last week staged a sit-in protest at the courthouse where the sole surviving hostage-taker is on trial.