The Trace is supposed to report any magical activity from a young wizard.

But as is it said here, it actually reports the magic done around the young wizard, without knowing who really did the spell.

The Ministry trusts magical parents to properly discipline their children if they perform magic due to the fact that the parents' own magic will constantly interfere with the Trace. Children who grow up in the Muggle world, such as Harry Potter, are more closely monitored — any magic that was performed at or near 4 Privet Drive was assumed to have been caused by him because he was the only known magical person living in his neighbourhood. Thus, when the house-elf Dobby used magic at that location, the Ministry blamed Harry.

In the Order of the Phoenix, when Harry is about to leave, Tonks helps him pack his belongings.

"Don't be stupid, it'll be much quicker if I - pack" cried Tonks, waving her wand in a long, sweeping movement over the floor".

And a few moments later :

"... That could do with a bit of cleaning, too - Scourgify..."

 

"Locomotor Trunk."

Harry is already in trouble for using a Patronus Charm (first letter from the ministry) :

We have received intelligence that you performed the Patronus Charm at twenty-three minutes past nine this evening in a Muggle-inhabited area and in the presence of a Muggle. The severity of this breach of the Decree for the Reasonable Restriction of Underage Sorcery has resulted in your expulsion from Hogwarts School of Witchcraft and Wizardry.

 

...

 

As you have already received an official warning for a previous offense under section 13 of the International Confederation of Wizards’ Statute of Secrecy, we regret to inform you that your presence is required at a disciplinary hearing at the Ministry of Magic at 9 A.M. on August 12th.

It seems he is in trouble just for using a spell, not because it was done outside and in the presence of muggle.

So wouldn't the spells used by Tonks be the perfect excuse to expel him for good ?

EDIT : I'm adding that it seems they want to be discreet. I don't see them warning the ministry that they are going to use magic, because even that Kingsley, Arthur and Tonks are associated is a secret.

“How’re we getting — wherever we’re going?” Harry asked.

 

“Brooms,” said Lupin. “Only way. You’re too young to Apparate, they’ll be watching the Floo Network, and it’s more than our life’s worth to set up an unauthorized Portkey.”

The Trace is supposed to report any magical activity from a young wizard.

But as is it said here, it actually reports the magic done around the young wizard, without knowing who really did the spell.

The Ministry trusts magical parents to properly discipline their children if they perform magic due to the fact that the parents' own magic will constantly interfere with the Trace. Children who grow up in the Muggle world, such as Harry Potter, are more closely monitored — any magic that was performed at or near 4 Privet Drive was assumed to have been caused by him because he was the only known magical person living in his neighbourhood. Thus, when the house-elf Dobby used magic at that location, the Ministry blamed Harry.

In the Order of the Phoenix, when Harry is about to leave, Tonks helps him pack his belongings.

"Don't be stupid, it'll be much quicker if I - pack" cried Tonks, waving her wand in a long, sweeping movement over the floor".

And a few moments later :

"... That could do with a bit of cleaning, too - Scourgify..."

"Locomotor Trunk."

Harry is already in trouble for using a Patronus Charm (first letter from the ministry) :

We have received intelligence that you performed the Patronus Charm at twenty-three minutes past nine this evening in a Muggle-inhabited area and in the presence of a Muggle. The severity of this breach of the Decree for the Reasonable Restriction of Underage Sorcery has resulted in your expulsion from Hogwarts School of Witchcraft and Wizardry.

...

As you have already received an official warning for a previous offense under section 13 of the International Confederation of Wizards’ Statute of Secrecy, we regret to inform you that your presence is required at a disciplinary hearing at the Ministry of Magic at 9 A.M. on August 12th.

It seems he is in trouble just for using a spell, not because it was done outside and in the presence of muggle.

So wouldn't the spells used by Tonks be the perfect excuse to expel him for good ?

EDIT : I'm adding that it seems they want to be discreet. I don't see them warning the ministry that they are going to use magic, because even that Kingsley, Arthur and Tonks are associated is a secret.

“How’re we getting — wherever we’re going?” Harry asked.

“Brooms,” said Lupin. “Only way. You’re too young to Apparate, they’ll be watching the Floo Network, and it’s more than our life’s worth to set up an unauthorized Portkey.”

The Trace is supposed to report any magical activity from a young wizard.

But as is it said here, it actually reports the magic done around the young wizard, without knowing who really did the spell.

The Ministry trusts magical parents to properly discipline their children if they perform magic due to the fact that the parents' own magic will constantly interfere with the Trace. Children who grow up in the Muggle world, such as Harry Potter, are more closely monitored — any magic that was performed at or near 4 Privet Drive was assumed to have been caused by him because he was the only known magical person living in his neighbourhood. Thus, when the house-elf Dobby used magic at that location, the Ministry blamed Harry.

In the Order of the Phoenix, when Harry is about to leave, Tonks helps him pack his belongings.

"Don't be stupid, it'll be much quicker if I - pack" cried Tonks, waving her wand in a long, sweeping movement over the floor".

And a few moments later :

"... That could do with a bit of cleaning, too - Scourgify..."

"Locomotor Trunk."

Harry is already in trouble for using a Patronus Charm (first letter from the ministry) :

We have received intelligence that you performed the Patronus Charm at twenty-three minutes past nine this evening in a Muggle-inhabited area and in the presence of a Muggle. The severity of this breach of the Decree for the Reasonable Restriction of Underage Sorcery has resulted in your expulsion from Hogwarts School of Witchcraft and Wizardry.

...

As you have already received an official warning for a previous offense under section 13 of the International Confederation of Wizards’ Statute of Secrecy, we regret to inform you that your presence is required at a disciplinary hearing at the Ministry of Magic at 9 A.M. on August 12th.

It seems he is in trouble just for using a spell, not because it was done outside and in the presence of muggle.

So wouldn't the spells used by Tonks be the perfect excuse to expel him for good ?

EDIT : I'm adding that it seems they want to be discrete. I don't see them warning the ministry that they are going to use magic, because even that Kingsley, Arthur and Tonks are associated is a secret.

“How’re we getting — wherever we’re going?” Harry asked.

“Brooms,” said Lupin. “Only way. You’re too young to Apparate, they’ll be watching the Floo Network, and it’s more than our life’s worth to set up an unauthorized Portkey.”

The Trace is supposed to report any magical activity from a young wizard.

But as is it said here, it actually reports the magic done around the young wizard, without knowing who really did the spell.

The Ministry trusts magical parents to properly discipline their children if they perform magic due to the fact that the parents' own magic will constantly interfere with the Trace. Children who grow up in the Muggle world, such as Harry Potter, are more closely monitored — any magic that was performed at or near 4 Privet Drive was assumed to have been caused by him because he was the only known magical person living in his neighbourhood. Thus, when the house-elf Dobby used magic at that location, the Ministry blamed Harry.

In the Order of the Phoenix, when Harry is about to leave, Tonks helps him pack his belongings.

"Don't be stupid, it'll be much quicker if I - pack" cried Tonks, waving her wand in a long, sweeping movement over the floor".

And a few moments later :

"... That could do with a bit of cleaning, too - Scourgify..."

"Locomotor Trunk."

Harry is already in trouble for using a Patronus Charm (first letter from the ministry) :

We have received intelligence that you performed the Patronus Charm at twenty-three minutes past nine this evening in a Muggle-inhabited area and in the presence of a Muggle. The severity of this breach of the Decree for the Reasonable Restriction of Underage Sorcery has resulted in your expulsion from Hogwarts School of Witchcraft and Wizardry.

...

As you have already received an official warning for a previous offense under section 13 of the International Confederation of Wizards’ Statute of Secrecy, we regret to inform you that your presence is required at a disciplinary hearing at the Ministry of Magic at 9 A.M. on August 12th.

It seems he is in trouble just for using a spell, not because it was done outside and in the presence of muggle.

So wouldn't the spells used by Tonks be the perfect excuse to expel him for good ?

EDIT : I'm adding that it seems they want to be discreet. I don't see them warning the ministry that they are going to use magic, because even that Kingsley, Arthur and Tonks are associated is a secret.

“How’re we getting — wherever we’re going?” Harry asked.

“Brooms,” said Lupin. “Only way. You’re too young to Apparate, they’ll be watching the Floo Network, and it’s more than our life’s worth to set up an unauthorized Portkey.”